[llvm] a4d6c7d - [InstSimplify] Fold LoadInst for uniform constant global variables
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Mon Feb 20 00:44:01 PST 2023
Author: Kohei Asano
Date: 2023-02-20T09:43:52+01:00
New Revision: a4d6c7dd99cbf1c802c633dc9f73a69131b03fe6
URL: https://github.com/llvm/llvm-project/commit/a4d6c7dd99cbf1c802c633dc9f73a69131b03fe6
DIFF: https://github.com/llvm/llvm-project/commit/a4d6c7dd99cbf1c802c633dc9f73a69131b03fe6.diff
LOG: [InstSimplify] Fold LoadInst for uniform constant global variables
Fold LoadInst for uniformly initialized constants, even if there
are non-constant GEP indices.
Goal proof: https://alive2.llvm.org/ce/z/oZtVby
Motivated by https://github.com/rust-lang/rust/issues/107208
Differential Revision: https://reviews.llvm.org/D144184
Added:
Modified:
llvm/lib/Analysis/InstructionSimplify.cpp
llvm/test/Transforms/InstSimplify/load.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 38dc5fb3ee0e..9f294dfb4f20 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -6586,6 +6586,12 @@ static Value *simplifyLoadInst(LoadInst *LI, Value *PtrOp,
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);
diff --git a/llvm/test/Transforms/InstSimplify/load.ll b/llvm/test/Transforms/InstSimplify/load.ll
index 40ce6f7d4dfc..21a6452960ad 100644
--- a/llvm/test/Transforms/InstSimplify/load.ll
+++ b/llvm/test/Transforms/InstSimplify/load.ll
@@ -48,9 +48,7 @@ define <3 x float> @load_vec3() {
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 i32 @load_gep_const_zero_array(i64 %idx) {
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
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