Revert "[InstCombine] propagate 'nsw' on pointer difference of 'inbounds' geps (PR47430)"
This reverts commit 324a53205a3af979e3de109fdd52f91781816cba.
On closer examination of at least one of the test diffs,
this does not appear to be correct in all cases. Even the
existing 'nsw' creation may be wrong based on this example:
https://alive2.llvm.org/ce/z/uL4Hw9
https://alive2.llvm.org/ce/z/fJMKQS
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index a5dd8f6..5ce32bc 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1671,12 +1671,11 @@
I->getOpcode() == Instruction::Mul)
I->setHasNoUnsignedWrap();
- // If we have a 2nd GEP of the same base pointer, subtract the offsets.
- // If both GEPs are inbounds, then the subtract does not have signed overflow.
+ // If we had a constant expression GEP on the other side offsetting the
+ // pointer, subtract it from the offset we have.
if (GEP2) {
Value *Offset = EmitGEPOffset(GEP2);
- Result = Builder.CreateSub(Result, Offset, "gepdiff", /* NUW */ false,
- GEP1->isInBounds() && GEP2->isInBounds());
+ Result = Builder.CreateSub(Result, Offset, "gepdiff");
}
// If we have p - gep(p, ...) then we have to negate the result.
diff --git a/llvm/test/Transforms/InstCombine/sub-gep.ll b/llvm/test/Transforms/InstCombine/sub-gep.ll
index ee0c9ff..ce965743 100644
--- a/llvm/test/Transforms/InstCombine/sub-gep.ll
+++ b/llvm/test/Transforms/InstCombine/sub-gep.ll
@@ -245,7 +245,7 @@
define i64 @test25(i8* %P, i64 %A){
; CHECK-LABEL: @test25(
; CHECK-NEXT: [[B_IDX:%.*]] = shl nsw i64 [[A:%.*]], 1
-; CHECK-NEXT: [[GEPDIFF:%.*]] = add nsw i64 [[B_IDX]], -84
+; CHECK-NEXT: [[GEPDIFF:%.*]] = add i64 [[B_IDX]], -84
; CHECK-NEXT: ret i64 [[GEPDIFF]]
;
%B = getelementptr inbounds [42 x i16], [42 x i16]* @Arr, i64 0, i64 %A
@@ -260,7 +260,7 @@
; CHECK-LABEL: @test25_as1(
; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[A:%.*]] to i16
; CHECK-NEXT: [[B_IDX:%.*]] = shl nsw i16 [[TMP1]], 1
-; CHECK-NEXT: [[GEPDIFF:%.*]] = add nsw i16 [[B_IDX]], -84
+; CHECK-NEXT: [[GEPDIFF:%.*]] = add i16 [[B_IDX]], -84
; CHECK-NEXT: ret i16 [[GEPDIFF]]
;
%B = getelementptr inbounds [42 x i16], [42 x i16] addrspace(1)* @Arr_as1, i64 0, i64 %A
@@ -272,7 +272,7 @@
define i64 @test30(i8* %foo, i64 %i, i64 %j) {
; CHECK-LABEL: @test30(
; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i64 [[I:%.*]], 2
-; CHECK-NEXT: [[GEPDIFF:%.*]] = sub nsw i64 [[GEP1_IDX]], [[J:%.*]]
+; CHECK-NEXT: [[GEPDIFF:%.*]] = sub i64 [[GEP1_IDX]], [[J:%.*]]
; CHECK-NEXT: ret i64 [[GEPDIFF]]
;
%bit = bitcast i8* %foo to i32*
@@ -287,7 +287,7 @@
define i16 @test30_as1(i8 addrspace(1)* %foo, i16 %i, i16 %j) {
; CHECK-LABEL: @test30_as1(
; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i16 [[I:%.*]], 2
-; CHECK-NEXT: [[GEPDIFF:%.*]] = sub nsw i16 [[GEP1_IDX]], [[J:%.*]]
+; CHECK-NEXT: [[GEPDIFF:%.*]] = sub i16 [[GEP1_IDX]], [[J:%.*]]
; CHECK-NEXT: ret i16 [[GEPDIFF]]
;
%bit = bitcast i8 addrspace(1)* %foo to i32 addrspace(1)*
@@ -299,11 +299,9 @@
ret i16 %sub
}
-; Inbounds translates to 'nsw' on sub
-
define i64 @gep_diff_both_inbounds(i8* %foo, i64 %i, i64 %j) {
; CHECK-LABEL: @gep_diff_both_inbounds(
-; CHECK-NEXT: [[GEPDIFF:%.*]] = sub nsw i64 [[I:%.*]], [[J:%.*]]
+; CHECK-NEXT: [[GEPDIFF:%.*]] = sub i64 [[I:%.*]], [[J:%.*]]
; CHECK-NEXT: ret i64 [[GEPDIFF]]
;
%gep1 = getelementptr inbounds i8, i8* %foo, i64 %i
@@ -314,8 +312,6 @@
ret i64 %sub
}
-; Negative test for 'nsw' - both geps must be inbounds
-
define i64 @gep_diff_first_inbounds(i8* %foo, i64 %i, i64 %j) {
; CHECK-LABEL: @gep_diff_first_inbounds(
; CHECK-NEXT: [[GEPDIFF:%.*]] = sub i64 [[I:%.*]], [[J:%.*]]
@@ -329,8 +325,6 @@
ret i64 %sub
}
-; Negative test for 'nsw' - both geps must be inbounds
-
define i64 @gep_diff_second_inbounds(i8* %foo, i64 %i, i64 %j) {
; CHECK-LABEL: @gep_diff_second_inbounds(
; CHECK-NEXT: [[GEPDIFF:%.*]] = sub i64 [[I:%.*]], [[J:%.*]]
diff --git a/llvm/test/Transforms/InstCombine/sub.ll b/llvm/test/Transforms/InstCombine/sub.ll
index 0940a08..98d8a9e 100644
--- a/llvm/test/Transforms/InstCombine/sub.ll
+++ b/llvm/test/Transforms/InstCombine/sub.ll
@@ -1077,7 +1077,7 @@
; CHECK-LABEL: @test58(
; CHECK-NEXT: [[GEP1_OFFS:%.*]] = add i64 [[I:%.*]], 4200
; CHECK-NEXT: [[GEP2_OFFS:%.*]] = add i64 [[J:%.*]], 4200
-; CHECK-NEXT: [[GEPDIFF:%.*]] = sub nsw i64 [[GEP1_OFFS]], [[GEP2_OFFS]]
+; CHECK-NEXT: [[GEPDIFF:%.*]] = sub i64 [[GEP1_OFFS]], [[GEP2_OFFS]]
; CHECK-NEXT: ret i64 [[GEPDIFF]]
;
%gep1 = getelementptr inbounds [100 x [100 x i8]], [100 x [100 x i8]]* %foo, i64 0, i64 42, i64 %i