[llvm] 4a2a639 - [InstCombine] Relax one-use check for icmp of gep fold

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2023-12-08T15:45:58+01:00
New Revision: 4a2a6397f11da7c15a73d19fb1e6c9dcd1ceb5af

URL: https://github.com/llvm/llvm-project/commit/4a2a6397f11da7c15a73d19fb1e6c9dcd1ceb5af
DIFF: https://github.com/llvm/llvm-project/commit/4a2a6397f11da7c15a73d19fb1e6c9dcd1ceb5af.diff

LOG: [InstCombine] Relax one-use check for icmp of gep fold

Instead of checking whether the GEP as a whole is constant, only
check whether it has constant incides. This matches what we do in
other places in this code.

This has little practical impact, because it is mostly already
handled through other cases anyway. We see a difference for
non-inbounds equality comparisons.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/test/Transforms/InstCombine/icmp-gep.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index b1c70396e69aa2..e42e011bd43615 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -812,8 +812,8 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
     // Only lower this if the icmp is the only user of the GEP or if we expect
     // the result to fold to a constant!
     if ((GEPsInBounds || CmpInst::isEquality(Cond)) &&
-        (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
-        (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
+        (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
+        (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse())) {
       // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2)  --->  (OFFSET1 cmp OFFSET2)
       Value *L = EmitGEPOffset(GEPLHS);
       Value *R = EmitGEPOffset(GEPRHS);

diff  --git a/llvm/test/Transforms/InstCombine/icmp-gep.ll b/llvm/test/Transforms/InstCombine/icmp-gep.ll
index da5976f9653ae0..99c784d15eb30a 100644
--- a/llvm/test/Transforms/InstCombine/icmp-gep.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-gep.ll
@@ -431,9 +431,9 @@ define i1 @test60_extra_use_const_operands_inbounds(ptr %foo, i64 %i, i64 %j) {
 define i1 @test60_extra_use_const_operands_no_inbounds(ptr %foo, i64 %i, i64 %j) {
 ; CHECK-LABEL: @test60_extra_use_const_operands_no_inbounds(
 ; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr i32, ptr [[FOO:%.*]], i64 1
-; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr i16, ptr [[FOO]], i64 [[J:%.*]]
 ; CHECK-NEXT:    call void @use(ptr [[GEP1]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[GEP1]], [[GEP2]]
+; CHECK-NEXT:    [[GEP2_IDX_MASK:%.*]] = and i64 [[J:%.*]], 9223372036854775807
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[GEP2_IDX_MASK]], 2
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %gep1 = getelementptr i32, ptr %foo, i64 1