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

[Kohei Asano via Phabricator via llvm-commits]

khei4 updated this revision to Diff 498137.
khei4 added a comment.

Fix comments and add test cases.


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
@@ -3,8 +3,13 @@
 
 @zeroinit = constant {} zeroinitializer
 @poison = constant {} poison
+
+
 @constzeroarray = internal constant [4 x i32] zeroinitializer
+ at constzeroarrayi8 = internal constant [2 x i8] zeroinitializer
+
 @constarray = internal constant [4 x i32] [i32 1, i32 1, i32 1, i32 1]
+ at constarrayi8 = internal constant [2 x i8] [i8 1, i8 1]
 
 define i32 @crash_on_zeroinit() {
 ; CHECK-LABEL: @crash_on_zeroinit(
@@ -47,18 +52,40 @@
 ; CHECK-LABEL: @load_gep_const_zero_array(
 ; CHECK-NEXT:    ret i32 0
 ;
-  %gep = getelementptr inbounds [4 x i32], ptr @constzeroarray , i64 0, i64 %idx
+  %gep = getelementptr inbounds [4 x i32], ptr @constzeroarray, i64 0, i64 %idx
   %load = load i32, ptr %gep
   ret i32 %load
 }
 
+define i8 @load_gep_const_zero_array_i8(i64 %idx) {
+; CHECK-LABEL: @load_gep_const_zero_array_i8(
+; CHECK-NEXT:    ret i8 0
+;
+  %gep1 = getelementptr inbounds i8, ptr @constzeroarrayi8, i64 0
+  %gep = getelementptr inbounds i8, ptr %gep1, i64 %idx
+  %load = load i8, ptr %gep
+  ret i8 %load
+}
+
 define i32 @load_gep_const_array(i64 %idx) {
 ; CHECK-LABEL: @load_gep_const_array(
 ; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds [4 x i32], ptr @constarray, i64 0, i64 [[IDX:%.*]]
 ; CHECK-NEXT:    [[LOAD:%.*]] = load i32, ptr [[GEP]], align 4
 ; CHECK-NEXT:    ret i32 [[LOAD]]
 ;
-  %gep = getelementptr inbounds [4 x i32], ptr @constarray , i64 0, i64 %idx
+  %gep = getelementptr inbounds [4 x i32], ptr @constarray, i64 0, i64 %idx
   %load = load i32, ptr %gep
   ret i32 %load
 }
+
+define i8 @load_gep_const_array_i8(i64 %idx) {
+; CHECK-LABEL: @load_gep_const_array_i8(
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds i8, ptr @constarrayi8, i64 [[IDX:%.*]]
+; CHECK-NEXT:    [[LOAD:%.*]] = load i8, ptr [[GEP]], align 1
+; CHECK-NEXT:    ret i8 [[LOAD]]
+;
+  %gep1 = getelementptr inbounds i8, ptr @constarrayi8, i64 0
+  %gep = getelementptr inbounds i8, ptr %gep1, i64 %idx
+  %load = load i8, ptr %gep
+  ret i8 %load
+}
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -6586,6 +6586,11 @@
   if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer())
     return nullptr;
 
+  // If GlobalVariable's initializer is uniform, then return the constant
+  // regardless 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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