[InstSimplify] Do not simplify freeze in `simplifyWithOpReplaced` (#91215)

See the LangRef:
> All uses of a value returned by the same ‘freeze’ instruction are
guaranteed to always observe the same value, while different ‘freeze’
instructions may yield different values.

It is incorrect to replace freezes with the simplified value.

Proof:
https://alive2.llvm.org/ce/z/3Dn9Cd
https://alive2.llvm.org/ce/z/Qyh5h6

Fixes https://github.com/llvm/llvm-project/issues/91178

(cherry picked from commit d085b42cbbefe79a41113abcd2b1e1f2a203acef)

Revert "[InstSimplify] Do not simplify freeze in `simplifyWithOpReplaced` (#91215)"

This reverts commit 1c2eb18d52976fef89972e89c52d2ec5ed7e4868.

[InstSimplify] Do not simplify freeze in `simplifyWithOpReplaced` (#91215)

See the LangRef:
> All uses of a value returned by the same ‘freeze’ instruction are
guaranteed to always observe the same value, while different ‘freeze’
instructions may yield different values.

It is incorrect to replace freezes with the simplified value.

Proof:
https://alive2.llvm.org/ce/z/3Dn9Cd
https://alive2.llvm.org/ce/z/Qyh5h6

Fixes https://github.com/llvm/llvm-project/issues/91178

(cherry picked from commit d085b42cbbefe79a41113abcd2b1e1f2a203acef)

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 72b6dfa181e86d044fd6b91e336ad6c24b5417aa..8dcffe45c644b13e97cea52605d67ea97823ee88 100644 (file)
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4322,6 +4322,10 @@ static Value *simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
   if (match(I, m_Intrinsic<Intrinsic::is_constant>()))
     return nullptr;
 
+  // Don't simplify freeze.
+  if (isa<FreezeInst>(I))
+    return nullptr;
+
   // Replace Op with RepOp in instruction operands.
   SmallVector<Value *, 8> NewOps;
   bool AnyReplaced = false;

diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index 10ab1fe118348c396fbda34f2a262bb6fece3b76..9ac35745742bb2b7a71a4869310428b0679939f8 100644 (file)
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -5183,3 +5183,18 @@ entry:
   %cmp = icmp eq i8 %add2, %add1
   ret i1 %cmp
 }
+
+define i1 @icmp_freeze_sext(i16 %x, i16 %y) {
+; CHECK-LABEL: @icmp_freeze_sext(
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp uge i16 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[CMP1_FR:%.*]] = freeze i1 [[CMP1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i16 [[Y]], 0
+; CHECK-NEXT:    [[CMP2:%.*]] = or i1 [[TMP1]], [[CMP1_FR]]
+; CHECK-NEXT:    ret i1 [[CMP2]]
+;
+  %cmp1 = icmp uge i16 %x, %y
+  %ext = sext i1 %cmp1 to i16
+  %ext.fr = freeze i16 %ext
+  %cmp2 = icmp uge i16 %ext.fr, %y
+  ret i1 %cmp2
+}

diff --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index 888e7d28f78afbf6cb0d17498733665db6af2c3c..1909f9b0daf8230b1721d9ae9c55a5511042e029 100644 (file)
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -3708,3 +3708,35 @@ define i32 @src_select_xxory_eq0_xorxy_y(i32 %x, i32 %y) {
   %cond = select i1 %xor0, i32 %xor, i32 %y
   ret i32 %cond
 }
+
+define i8 @test_replace_freeze_multiuse(i1 %x, i8 %y) {
+; CHECK-LABEL: @test_replace_freeze_multiuse(
+; CHECK-NEXT:    [[EXT:%.*]] = zext i1 [[X:%.*]] to i8
+; CHECK-NEXT:    [[SHL:%.*]] = shl nuw i8 [[EXT]], [[Y:%.*]]
+; CHECK-NEXT:    [[SHL_FR:%.*]] = freeze i8 [[SHL]]
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[X]], i8 0, i8 [[SHL_FR]]
+; CHECK-NEXT:    [[ADD:%.*]] = add i8 [[SHL_FR]], [[SEL]]
+; CHECK-NEXT:    ret i8 [[ADD]]
+;
+  %ext = zext i1 %x to i8
+  %shl = shl nuw i8 %ext, %y
+  %shl.fr = freeze i8 %shl
+  %sel = select i1 %x, i8 0, i8 %shl.fr
+  %add = add i8 %shl.fr, %sel
+  ret i8 %add
+}
+
+define i8 @test_replace_freeze_oneuse(i1 %x, i8 %y) {
+; CHECK-LABEL: @test_replace_freeze_oneuse(
+; CHECK-NEXT:    [[EXT:%.*]] = zext i1 [[X:%.*]] to i8
+; CHECK-NEXT:    [[SHL:%.*]] = shl nuw i8 [[EXT]], [[Y:%.*]]
+; CHECK-NEXT:    [[SHL_FR:%.*]] = freeze i8 [[SHL]]
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[X]], i8 0, i8 [[SHL_FR]]
+; CHECK-NEXT:    ret i8 [[SEL]]
+;
+  %ext = zext i1 %x to i8
+  %shl = shl nuw i8 %ext, %y
+  %shl.fr = freeze i8 %shl
+  %sel = select i1 %x, i8 0, i8 %shl.fr
+  ret i8 %sel
+}

diff --git a/llvm/test/Transforms/PGOProfile/chr.ll b/llvm/test/Transforms/PGOProfile/chr.ll
index 0551a171091ca7fb735c9e37d360a4f249467285..38e8f8536a19c022a0bbc9f255602de194a783a2 100644 (file)
--- a/llvm/test/Transforms/PGOProfile/chr.ll
+++ b/llvm/test/Transforms/PGOProfile/chr.ll
@@ -1298,11 +1298,12 @@ define i32 @test_chr_14(ptr %i, ptr %j, i32 %sum0, i1 %pred, i32 %z) !prof !14 {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[Z_FR:%.*]] = freeze i32 [[Z:%.*]]
 ; CHECK-NEXT:    [[I0:%.*]] = load i32, ptr [[I:%.*]], align 4
-; CHECK-NEXT:    [[V1:%.*]] = icmp eq i32 [[Z_FR]], 1
-; CHECK-NEXT:    br i1 [[V1]], label [[BB1:%.*]], label [[ENTRY_SPLIT_NONCHR:%.*]], !prof [[PROF15]]
+; CHECK-NEXT:    [[V1_NOT:%.*]] = icmp eq i32 [[Z_FR]], 1
+; CHECK-NEXT:    br i1 [[V1_NOT]], label [[BB1:%.*]], label [[ENTRY_SPLIT_NONCHR:%.*]], !prof [[PROF15]]
 ; CHECK:       entry.split.nonchr:
+; CHECK-NEXT:    [[PRED_FR:%.*]] = freeze i1 [[PRED:%.*]]
 ; CHECK-NEXT:    [[V0:%.*]] = icmp eq i32 [[Z_FR]], 0
-; CHECK-NEXT:    [[V3_NONCHR:%.*]] = and i1 [[V0]], [[PRED:%.*]]
+; CHECK-NEXT:    [[V3_NONCHR:%.*]] = and i1 [[V0]], [[PRED_FR]]
 ; CHECK-NEXT:    br i1 [[V3_NONCHR]], label [[BB0_NONCHR:%.*]], label [[BB1]], !prof [[PROF16]]
 ; CHECK:       bb0.nonchr:
 ; CHECK-NEXT:    call void @foo()