[AssumeBundles] preserve knowledge in DSE

Reviewers: jdoerfert

Reviewed By: jdoerfert

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D77404

diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index 7b0a877..f8a9f4f 100644 (file)
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -63,6 +63,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/AssumeBundleBuilder.h"
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
@@ -144,6 +145,7 @@ deleteDeadInstruction(Instruction *I, BasicBlock::iterator *BBI,
 
     // Try to preserve debug information attached to the dead instruction.
     salvageDebugInfoOrMarkUndef(*DeadInst);
+    salvageKnowledge(DeadInst);
 
     // This instruction is dead, zap it, in stages.  Start by removing it from
     // MemDep, which needs to know the operands and needs it to be in the
@@ -1729,6 +1731,7 @@ struct DSEState {
 
       // Try to preserve debug information attached to the dead instruction.
       salvageDebugInfo(*DeadInst);
+      salvageKnowledge(DeadInst);
 
       // Remove the Instruction from MSSA.
       if (MemoryAccess *MA = MSSA.getMemoryAccess(DeadInst)) {

diff --git a/llvm/test/Transforms/DeadStoreElimination/MSSA/simple-preservation.ll b/llvm/test/Transforms/DeadStoreElimination/MSSA/simple-preservation.ll
new file mode 100644 (file)
index 0000000..7786f74
--- /dev/null
+++ b/llvm/test/Transforms/DeadStoreElimination/MSSA/simple-preservation.ll
@@ -0,0 +1,17 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -aa-pipeline=basic-aa -passes=dse -enable-dse-memoryssa -enable-knowledge-retention -S | FileCheck %s
+
+target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128"
+
+define void @test1(i32* %Q, i32* %P) {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:    call void @llvm.assume(i1 true) [ "dereferenceable"(i32* [[Q:%.*]], i64 4), "nonnull"(i32* [[Q]]) ]
+; CHECK-NEXT:    call void @llvm.assume(i1 true) [ "dereferenceable"(i32* [[P:%.*]], i64 4), "nonnull"(i32* [[P]]) ]
+; CHECK-NEXT:    store i32 0, i32* [[P]]
+; CHECK-NEXT:    ret void
+;
+  %DEAD = load i32, i32* %Q
+  store i32 %DEAD, i32* %P
+  store i32 0, i32* %P
+  ret void
+}