[llvm] f08148e - [ConstProp] Fix folding of pointer icmp with signed predicates
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 8 08:14:11 PST 2021
Author: Nikita Popov
Date: 2021-03-08T17:12:12+01:00
New Revision: f08148e874088a07b972203a183db00de9c38a70
URL: https://github.com/llvm/llvm-project/commit/f08148e874088a07b972203a183db00de9c38a70
DIFF: https://github.com/llvm/llvm-project/commit/f08148e874088a07b972203a183db00de9c38a70.diff
LOG: [ConstProp] Fix folding of pointer icmp with signed predicates
While @g ugt null is always true (ignoring weak symbols),
@g sgt null is not necessarily the case -- that would imply that
it is forbidden to place globals in the high half of the address
space.
Added:
Modified:
llvm/lib/IR/ConstantFold.cpp
llvm/test/Transforms/InstSimplify/ConstProp/icmp-null.ll
Removed:
################################################################################
diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
index 3903d72ac7c3..2e0ea4c50e79 100644
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -1838,35 +1838,27 @@ static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2,
// If we are comparing a GEP to a null pointer, check to see if the base
// of the GEP equals the null pointer.
if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
- if (GV->hasExternalWeakLinkage())
- // Weak linkage GVals could be zero or not. We're comparing that
- // to null pointer so its greater-or-equal
- return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
- else
- // If its not weak linkage, the GVal must have a non-zero address
- // so the result is greater-than
- return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
+ // If its not weak linkage, the GVal must have a non-zero address
+ // so the result is greater-than
+ if (!GV->hasExternalWeakLinkage())
+ return ICmpInst::ICMP_UGT;
} else if (isa<ConstantPointerNull>(CE1Op0)) {
// If we are indexing from a null pointer, check to see if we have any
// non-zero indices.
for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
if (!CE1->getOperand(i)->isNullValue())
// Offsetting from null, must not be equal.
- return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
+ return ICmpInst::ICMP_UGT;
// Only zero indexes from null, must still be zero.
return ICmpInst::ICMP_EQ;
}
// Otherwise, we can't really say if the first operand is null or not.
} else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
if (isa<ConstantPointerNull>(CE1Op0)) {
- if (GV2->hasExternalWeakLinkage())
- // Weak linkage GVals could be zero or not. We're comparing it to
- // a null pointer, so its less-or-equal
- return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
- else
- // If its not weak linkage, the GVal must have a non-zero address
- // so the result is less-than
- return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
+ // If its not weak linkage, the GVal must have a non-zero address
+ // so the result is less-than
+ if (!GV2->hasExternalWeakLinkage())
+ return ICmpInst::ICMP_ULT;
} else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
if (GV == GV2) {
// If this is a getelementptr of the same global, then it must be
@@ -1876,7 +1868,7 @@ static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2,
assert(CE1->getNumOperands() == 2 &&
!CE1->getOperand(1)->isNullValue() &&
"Surprising getelementptr!");
- return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
+ return ICmpInst::ICMP_UGT;
} else {
if (CE1GEP->hasAllZeroIndices())
return areGlobalsPotentiallyEqual(GV, GV2);
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/icmp-null.ll b/llvm/test/Transforms/InstSimplify/ConstProp/icmp-null.ll
index 46fd8c4bfce8..41a64205633e 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/icmp-null.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/icmp-null.ll
@@ -110,7 +110,7 @@ define i1 @global_gep_ugt_null() {
define i1 @global_gep_sgt_null() {
; CHECK-LABEL: @global_gep_sgt_null(
-; CHECK-NEXT: ret i1 true
+; CHECK-NEXT: ret i1 icmp sgt ([2 x i32]* getelementptr inbounds ([2 x i32], [2 x i32]* @g, i64 1), [2 x i32]* null)
;
%gep = getelementptr inbounds [2 x i32], [2 x i32]* @g, i64 1
%cmp = icmp sgt [2 x i32]* %gep, null
@@ -137,7 +137,7 @@ define i1 @null_gep_ugt_null() {
define i1 @null_gep_sgt_null() {
; CHECK-LABEL: @null_gep_sgt_null(
-; CHECK-NEXT: ret i1 true
+; CHECK-NEXT: ret i1 icmp sgt (i8* getelementptr (i8, i8* null, i64 ptrtoint (i32* @g2 to i64)), i8* null)
;
%gep = getelementptr i8, i8* null, i64 ptrtoint (i32* @g2 to i64)
%cmp = icmp sgt i8* %gep, null
@@ -164,7 +164,7 @@ define i1 @null_gep_ult_global() {
define i1 @null_gep_slt_global() {
; CHECK-LABEL: @null_gep_slt_global(
-; CHECK-NEXT: ret i1 true
+; CHECK-NEXT: ret i1 icmp slt ([2 x i32]* getelementptr ([2 x i32], [2 x i32]* null, i64 ptrtoint (i32* @g2 to i64)), [2 x i32]* @g)
;
%gep = getelementptr [2 x i32], [2 x i32]* null, i64 ptrtoint (i32* @g2 to i64)
%cmp = icmp slt [2 x i32]* %gep, @g
@@ -191,7 +191,7 @@ define i1 @global_gep_ugt_global() {
define i1 @global_gep_sgt_global() {
; CHECK-LABEL: @global_gep_sgt_global(
-; CHECK-NEXT: ret i1 true
+; CHECK-NEXT: ret i1 icmp sgt ([2 x i32]* getelementptr inbounds ([2 x i32], [2 x i32]* @g, i64 1), [2 x i32]* @g)
;
%gep = getelementptr inbounds [2 x i32], [2 x i32]* @g, i64 1
%cmp = icmp sgt [2 x i32]* %gep, @g
@@ -209,7 +209,7 @@ define i1 @global_gep_ugt_global_neg_offset() {
define i1 @global_gep_sgt_global_neg_offset() {
; CHECK-LABEL: @global_gep_sgt_global_neg_offset(
-; CHECK-NEXT: ret i1 true
+; CHECK-NEXT: ret i1 icmp sgt ([2 x i32]* getelementptr ([2 x i32], [2 x i32]* @g, i64 -1), [2 x i32]* @g)
;
%gep = getelementptr [2 x i32], [2 x i32]* @g, i64 -1
%cmp = icmp sgt [2 x i32]* %gep, @g
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