[PATCH] D144184: [InstSimplify] fold LoadInst for uniformaly initialized constant global variables

[Nikita Popov via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGa4d6c7dd99cb: [InstSimplify] Fold LoadInst for uniform constant global variables (authored by khei4, committed by nikic).

Changed prior to commit:
  https://reviews.llvm.org/D144184?vs=498708&id=498750#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D144184/new/

https://reviews.llvm.org/D144184

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstSimplify/load.ll


Index: llvm/test/Transforms/InstSimplify/load.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/load.ll
+++ llvm/test/Transforms/InstSimplify/load.ll
@@ -48,9 +48,7 @@
 
 define i32 @load_gep_const_zero_array(i64 %idx) {
 ; CHECK-LABEL: @load_gep_const_zero_array(
-; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds [4 x i32], ptr @constzeroarray, i64 0, i64 [[IDX:%.*]]
-; CHECK-NEXT:    [[LOAD:%.*]] = load i32, ptr [[GEP]], align 4
-; CHECK-NEXT:    ret i32 [[LOAD]]
+; CHECK-NEXT:    ret i32 0
 ;
   %gep = getelementptr inbounds [4 x i32], ptr @constzeroarray, i64 0, i64 %idx
   %load = load i32, ptr %gep
@@ -59,10 +57,7 @@
 
 define i8 @load_i8_multi_gep_const_zero_array(i64 %idx1, i64 %idx2) {
 ; CHECK-LABEL: @load_i8_multi_gep_const_zero_array(
-; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr inbounds i8, ptr @constzeroarray, i64 [[IDX1:%.*]]
-; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds i8, ptr [[GEP1]], i64 [[IDX2:%.*]]
-; CHECK-NEXT:    [[LOAD:%.*]] = load i8, ptr [[GEP]], align 1
-; CHECK-NEXT:    ret i8 [[LOAD]]
+; CHECK-NEXT:    ret i8 0
 ;
   %gep1 = getelementptr inbounds i8, ptr @constzeroarray, i64 %idx1
   %gep = getelementptr inbounds i8, ptr %gep1, i64 %idx2
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -6586,6 +6586,12 @@
   if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer())
     return nullptr;
 
+  // If GlobalVariable's initializer is uniform, then return the constant
+  // regardless of its offset.
+  if (Constant *C =
+          ConstantFoldLoadFromUniformValue(GV->getInitializer(), LI->getType()))
+    return C;
+
   // Try to convert operand into a constant by stripping offsets while looking
   // through invariant.group intrinsics.
   APInt Offset(Q.DL.getIndexTypeSizeInBits(PtrOp->getType()), 0);


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