[PPCMergeStringPool] Avoid replacing constant with instruction (#88846)

String pool merging currently, for a reason that's not entirely clear to
me, tries to create GEP instructions instead of GEP constant expressions
when replacing constant references. It only uses constant expressions in
cases where this is required. However, it does not catch all cases where
such a requirement exists. For example, the landingpad catch clause has
to be a constant.

Fix this by always using the constant expression variant, which also
makes the implementation simpler.

Additionally, there are some edge cases where even replacement with a
constant GEP is not legal. The one I am aware of is the
llvm.eh.typeid.for intrinsic, so add a special case to forbid
replacements for it.

Fixes https://github.com/llvm/llvm-project/issues/88844.

(cherry picked from commit 3a3aeb8eba40e981d3a9ff92175f949c2f3d4434)

diff --git a/llvm/lib/Target/PowerPC/PPCMergeStringPool.cpp b/llvm/lib/Target/PowerPC/PPCMergeStringPool.cpp
index d9465e86d8966241d36e44826b9bc6da29e159f0..ebd876d50c44e39e2e7240b5f93ddc5284fb8c8f 100644 (file)
--- a/llvm/lib/Target/PowerPC/PPCMergeStringPool.cpp
+++ b/llvm/lib/Target/PowerPC/PPCMergeStringPool.cpp
@@ -23,6 +23,7 @@
 #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/ValueSymbolTable.h"
 #include "llvm/Pass.h"
@@ -116,9 +117,20 @@ private:
 // sure that they can be replaced.
 static bool hasReplaceableUsers(GlobalVariable &GV) {
   for (User *CurrentUser : GV.users()) {
-    // Instruction users are always valid.
-    if (isa<Instruction>(CurrentUser))
+    if (auto *I = dyn_cast<Instruction>(CurrentUser)) {
+      // Do not merge globals in exception pads.
+      if (I->isEHPad())
+        return false;
+
+      if (auto *II = dyn_cast<IntrinsicInst>(I)) {
+        // Some intrinsics require a plain global.
+        if (II->getIntrinsicID() == Intrinsic::eh_typeid_for)
+          return false;
+      }
+
+      // Other instruction users are always valid.
       continue;
+    }
 
     // We cannot replace GlobalValue users because they are not just nodes
     // in IR. To replace a user like this we would need to create a new
@@ -302,14 +314,6 @@ void PPCMergeStringPool::replaceUsesWithGEP(GlobalVariable *GlobalToReplace,
     Users.push_back(CurrentUser);
 
   for (User *CurrentUser : Users) {
-    Instruction *UserInstruction = dyn_cast<Instruction>(CurrentUser);
-    Constant *UserConstant = dyn_cast<Constant>(CurrentUser);
-
-    // At this point we expect that the user is either an instruction or a
-    // constant.
-    assert((UserConstant || UserInstruction) &&
-           "Expected the user to be an instruction or a constant.");
-
     // The user was not found so it must have been replaced earlier.
     if (!userHasOperand(CurrentUser, GlobalToReplace))
       continue;
@@ -318,38 +322,13 @@ void PPCMergeStringPool::replaceUsesWithGEP(GlobalVariable *GlobalToReplace,
     if (isa<GlobalValue>(CurrentUser))
       continue;
 
-    if (!UserInstruction) {
-      // User is a constant type.
-      Constant *ConstGEP = ConstantExpr::getInBoundsGetElementPtr(
-          PooledStructType, GPool, Indices);
-      UserConstant->handleOperandChange(GlobalToReplace, ConstGEP);
-      continue;
-    }
-
-    if (PHINode *UserPHI = dyn_cast<PHINode>(UserInstruction)) {
-      // GEP instructions cannot be added before PHI nodes.
-      // With getInBoundsGetElementPtr we create the GEP and then replace it
-      // inline into the PHI.
-      Constant *ConstGEP = ConstantExpr::getInBoundsGetElementPtr(
-          PooledStructType, GPool, Indices);
-      UserPHI->replaceUsesOfWith(GlobalToReplace, ConstGEP);
-      continue;
-    }
-    // The user is a valid instruction that is not a PHINode.
-    GetElementPtrInst *GEPInst =
-        GetElementPtrInst::Create(PooledStructType, GPool, Indices);
-    GEPInst->insertBefore(UserInstruction);
-
-    LLVM_DEBUG(dbgs() << "Inserting GEP before:\n");
-    LLVM_DEBUG(UserInstruction->dump());
-
+    Constant *ConstGEP = ConstantExpr::getInBoundsGetElementPtr(
+        PooledStructType, GPool, Indices);
     LLVM_DEBUG(dbgs() << "Replacing this global:\n");
     LLVM_DEBUG(GlobalToReplace->dump());
     LLVM_DEBUG(dbgs() << "with this:\n");
-    LLVM_DEBUG(GEPInst->dump());
-
-    // After the GEP is inserted the GV can be replaced.
-    CurrentUser->replaceUsesOfWith(GlobalToReplace, GEPInst);
+    LLVM_DEBUG(ConstGEP->dump());
+    GlobalToReplace->replaceAllUsesWith(ConstGEP);
   }
 }
 

diff --git a/llvm/test/CodeGen/PowerPC/mergeable-string-pool-exceptions.ll b/llvm/test/CodeGen/PowerPC/mergeable-string-pool-exceptions.ll
new file mode 100644 (file)
index 0000000..0489c74
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/mergeable-string-pool-exceptions.ll
@@ -0,0 +1,47 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; RUN: llc -mtriple=ppc64le-unknown-linux-gnu < %s | FileCheck %s
+
+@id = private unnamed_addr constant [4 x i8] c"@id\00", align 1
+@id2 = private unnamed_addr constant [5 x i8] c"@id2\00", align 1
+
+; Higher-aligned dummy to make sure it is first in the string pool.
+@dummy = private unnamed_addr constant [1 x i32] [i32 42], align 4
+
+define ptr @test1() personality ptr @__gnu_objc_personality_v0 {
+; CHECK-LABEL: test1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    mflr 0
+; CHECK-NEXT:    stdu 1, -32(1)
+; CHECK-NEXT:    std 0, 48(1)
+; CHECK-NEXT:    .cfi_def_cfa_offset 32
+; CHECK-NEXT:    .cfi_offset lr, 16
+; CHECK-NEXT:    addis 3, 2, .L__ModuleStringPool@toc@ha
+; CHECK-NEXT:    addi 3, 3, .L__ModuleStringPool@toc@l
+; CHECK-NEXT:    bl foo
+; CHECK-NEXT:    nop
+  invoke void @foo(ptr @dummy)
+          to label %cont unwind label %unwind
+
+cont:
+  unreachable
+
+unwind:
+  %lp = landingpad { ptr, i32 }
+          catch ptr @id
+  resume { ptr, i32 } %lp
+}
+
+define i32 @test2() personality ptr @__gnu_objc_personality_v0 {
+; CHECK-LABEL: test2:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    li 3, 1
+; CHECK-NEXT:    blr
+  %id = tail call i32 @llvm.eh.typeid.for(ptr @id2)
+  ret i32 %id
+}
+
+declare i32 @__gnu_objc_personality_v0(...)
+
+declare i32 @llvm.eh.typeid.for(ptr)
+
+declare void @foo()

diff --git a/llvm/test/CodeGen/PowerPC/mergeable-string-pool-large.ll b/llvm/test/CodeGen/PowerPC/mergeable-string-pool-large.ll
index b13b01b416e64e065f99c972abed1209a930cc8f..b182763ccc1462496f9eb3934561ace0180f7767 100644 (file)
--- a/llvm/test/CodeGen/PowerPC/mergeable-string-pool-large.ll
+++ b/llvm/test/CodeGen/PowerPC/mergeable-string-pool-large.ll
@@ -319,16 +319,16 @@ define dso_local signext i32 @array0() local_unnamed_addr #0 {
 ; AIX32-NEXT:    mflr r0
 ; AIX32-NEXT:    stwu r1, -96(r1)
 ; AIX32-NEXT:    lis r6, 0
-; AIX32-NEXT:    lwz r4, L..C0(r2) # @__ModuleStringPool
-; AIX32-NEXT:    li r5, 12
+; AIX32-NEXT:    lwz r5, L..C0(r2) # @__ModuleStringPool
+; AIX32-NEXT:    li r4, 12
 ; AIX32-NEXT:    addi r3, r1, 64
 ; AIX32-NEXT:    stw r0, 104(r1)
 ; AIX32-NEXT:    ori r7, r6, 35596
-; AIX32-NEXT:    rlwimi r5, r3, 0, 30, 27
-; AIX32-NEXT:    lxvw4x vs0, r4, r7
-; AIX32-NEXT:    stxvw4x vs0, 0, r5
-; AIX32-NEXT:    ori r5, r6, 35584
-; AIX32-NEXT:    lxvw4x vs0, r4, r5
+; AIX32-NEXT:    rlwimi r4, r3, 0, 30, 27
+; AIX32-NEXT:    lxvw4x vs0, r5, r7
+; AIX32-NEXT:    stxvw4x vs0, 0, r4
+; AIX32-NEXT:    ori r4, r6, 35584
+; AIX32-NEXT:    lxvw4x vs0, r5, r4
 ; AIX32-NEXT:    stxvw4x vs0, 0, r3
 ; AIX32-NEXT:    bl .calleeInt[PR]
 ; AIX32-NEXT:    nop

diff --git a/llvm/test/CodeGen/PowerPC/mergeable-string-pool-pass-only.mir b/llvm/test/CodeGen/PowerPC/mergeable-string-pool-pass-only.mir
index e2fb0ced8f3490ec05592e9888d33eb85fe26f2f..3d8afb604fd3cae427efdb9da1cc1709628d38a4 100644 (file)
--- a/llvm/test/CodeGen/PowerPC/mergeable-string-pool-pass-only.mir
+++ b/llvm/test/CodeGen/PowerPC/mergeable-string-pool-pass-only.mir
@@ -35,8 +35,7 @@
     ret i32 %call
 
   ; CHECK-LABEL: test1
-  ; CHECK:         %0 = getelementptr { [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 6
-  ; CHECK:         tail call signext i32 @calleeStr
+  ; CHECK:         %call = tail call signext i32 @calleeStr(ptr noundef nonnull getelementptr inbounds ({ [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 6))
   }
 
   define dso_local signext i32 @test2() local_unnamed_addr #0 {
@@ -49,7 +48,7 @@
     ret i32 %call
 
   ; CHECK-LABEL: test2
-  ; CHECK:         %0 = getelementptr { [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 2
+  ; CHECK:         call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 4 dereferenceable(24) %A, ptr noundef nonnull align 4 dereferenceable(24) getelementptr inbounds ({ [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 2), i64 24, i1 false)
   ; CHECK:         call signext i32 @calleeInt
   }
 
@@ -62,7 +61,7 @@
     call void @llvm.lifetime.end.p0(i64 28, ptr nonnull %A) #0
     ret i32 %call
   ; CHECK-LABEL: test3
-  ; CHECK:         %0 = getelementptr { [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 4
+  ; CHECK:         call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 4 dereferenceable(28) %A, ptr noundef nonnull align 4 dereferenceable(28) getelementptr inbounds ({ [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 4), i64 28, i1 false)
   ; CHECK:         call signext i32 @calleeFloat
   }
 
@@ -75,7 +74,7 @@
     call void @llvm.lifetime.end.p0(i64 56, ptr nonnull %A) #0
     ret i32 %call
   ; CHECK-LABEL: test4
-  ; CHECK:         %0 = getelementptr { [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 0
+  ; CHECK:         call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 8 dereferenceable(56) %A, ptr noundef nonnull align 8 dereferenceable(56) @__ModuleStringPool, i64 56, i1 false)
   ; CHECK:         call signext i32 @calleeDouble
   }
 
@@ -102,11 +101,10 @@
     call void @llvm.lifetime.end.p0(i64 24, ptr nonnull %B) #0
     ret i32 %add7
   ; CHECK-LABEL: test5
-  ; CHECK:         %0 = getelementptr { [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 3
-  ; CHECK:         %1 = getelementptr { [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 5
-  ; CHECK:         %2 = getelementptr { [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 1
-  ; CHECK:         %3 = getelementptr { [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 7
-  ; CHECK:         call signext i32 @calleeStr
+  ; CHECK:         call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 4 dereferenceable(24) %B, ptr noundef nonnull align 4 dereferenceable(24) getelementptr inbounds ({ [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 3), i64 24, i1 false)
+  ; CHECK:         call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 4 dereferenceable(28) %C, ptr noundef nonnull align 4 dereferenceable(28) getelementptr inbounds ({ [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 5), i64 28, i1 false)
+  ; CHECK:         call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 8 dereferenceable(56) %D, ptr noundef nonnull align 8 dereferenceable(56) getelementptr inbounds ({ [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 1), i64 56, i1 false)
+  ; CHECK:         call signext i32 @calleeStr(ptr noundef nonnull getelementptr inbounds ({ [7 x double], [7 x double], [6 x i32], [6 x i32], [7 x float], [7 x float], [8 x i8], [16 x i8] }, ptr @__ModuleStringPool, i32 0, i32 7))
   ; CHECK:         call signext i32 @calleeInt
   ; CHECK:         call signext i32 @calleeFloat
   ; CHECK:         call signext i32 @calleeDouble

diff --git a/llvm/test/CodeGen/PowerPC/mergeable-string-pool.ll b/llvm/test/CodeGen/PowerPC/mergeable-string-pool.ll
index a6c5057dde57d3f1f9428d74a5923be4e24c410a..7ccdaaf91136bb5843d2452a45829af78875b109 100644 (file)
--- a/llvm/test/CodeGen/PowerPC/mergeable-string-pool.ll
+++ b/llvm/test/CodeGen/PowerPC/mergeable-string-pool.ll
@@ -398,16 +398,16 @@ define dso_local signext i32 @array1() local_unnamed_addr #0 {
 ; AIX32:       # %bb.0: # %entry
 ; AIX32-NEXT:    mflr r0
 ; AIX32-NEXT:    stwu r1, -96(r1)
-; AIX32-NEXT:    lwz r4, L..C0(r2) # @__ModuleStringPool
+; AIX32-NEXT:    lwz r5, L..C0(r2) # @__ModuleStringPool
 ; AIX32-NEXT:    li r6, 372
-; AIX32-NEXT:    li r5, 12
+; AIX32-NEXT:    li r4, 12
 ; AIX32-NEXT:    addi r3, r1, 64
 ; AIX32-NEXT:    stw r0, 104(r1)
-; AIX32-NEXT:    rlwimi r5, r3, 0, 30, 27
-; AIX32-NEXT:    lxvw4x vs0, r4, r6
-; AIX32-NEXT:    stxvw4x vs0, 0, r5
-; AIX32-NEXT:    li r5, 360
-; AIX32-NEXT:    lxvw4x vs0, r4, r5
+; AIX32-NEXT:    rlwimi r4, r3, 0, 30, 27
+; AIX32-NEXT:    lxvw4x vs0, r5, r6
+; AIX32-NEXT:    stxvw4x vs0, 0, r4
+; AIX32-NEXT:    li r4, 360
+; AIX32-NEXT:    lxvw4x vs0, r5, r4
 ; AIX32-NEXT:    stxvw4x vs0, 0, r3
 ; AIX32-NEXT:    bl .calleeInt[PR]
 ; AIX32-NEXT:    nop