[PATCH] D150378: [Instsimplfy] X == Y ? 0 : X - Y --> X - Y
Jun Zhang via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue May 16 04:16:52 PDT 2023
This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGa47b56f4ef83: [Instsimplfy] X == Y ? 0 : X - Y --> X - Y (authored by junaire).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D150378/new/
https://reviews.llvm.org/D150378
Files:
llvm/lib/Analysis/InstructionSimplify.cpp
llvm/test/Transforms/InstSimplify/select.ll
Index: llvm/test/Transforms/InstSimplify/select.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/select.ll
+++ llvm/test/Transforms/InstSimplify/select.ll
@@ -1441,10 +1441,8 @@
define i8 @select_sub_cmp(i8 %0, i8 %1) {
; CHECK-LABEL: @select_sub_cmp(
-; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i8 [[TMP1:%.*]], [[TMP0:%.*]]
-; CHECK-NEXT: [[TMP4:%.*]] = sub nsw i8 [[TMP1]], [[TMP0]]
-; CHECK-NEXT: [[TMP5:%.*]] = select i1 [[TMP3]], i8 0, i8 [[TMP4]]
-; CHECK-NEXT: ret i8 [[TMP5]]
+; CHECK-NEXT: [[TMP3:%.*]] = sub nsw i8 [[TMP1:%.*]], [[TMP0:%.*]]
+; CHECK-NEXT: ret i8 [[TMP3]]
;
%3 = icmp eq i8 %1, %0
%4 = sub nsw i8 %1, %0
@@ -1454,10 +1452,8 @@
define <2 x i8> @select_sub_cmp_vec(<2 x i8> %0, <2 x i8> %1) {
; CHECK-LABEL: @select_sub_cmp_vec(
-; CHECK-NEXT: [[TMP3:%.*]] = icmp eq <2 x i8> [[TMP1:%.*]], [[TMP0:%.*]]
-; CHECK-NEXT: [[TMP4:%.*]] = sub nsw <2 x i8> [[TMP1]], [[TMP0]]
-; CHECK-NEXT: [[TMP5:%.*]] = select <2 x i1> [[TMP3]], <2 x i8> zeroinitializer, <2 x i8> [[TMP4]]
-; CHECK-NEXT: ret <2 x i8> [[TMP5]]
+; CHECK-NEXT: [[TMP3:%.*]] = sub nsw <2 x i8> [[TMP1:%.*]], [[TMP0:%.*]]
+; CHECK-NEXT: ret <2 x i8> [[TMP3]]
;
%3 = icmp eq <2 x i8> %1, %0
%4 = sub nsw <2 x i8> %1, %0
@@ -1467,10 +1463,8 @@
define i8 @select_sub_cmp_swap(i8 %0, i8 %1) {
; CHECK-LABEL: @select_sub_cmp_swap(
-; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i8 [[TMP1:%.*]], [[TMP0:%.*]]
-; CHECK-NEXT: [[TMP4:%.*]] = sub nsw i8 [[TMP0]], [[TMP1]]
-; CHECK-NEXT: [[TMP5:%.*]] = select i1 [[TMP3]], i8 0, i8 [[TMP4]]
-; CHECK-NEXT: ret i8 [[TMP5]]
+; CHECK-NEXT: [[TMP3:%.*]] = sub nsw i8 [[TMP0:%.*]], [[TMP1:%.*]]
+; CHECK-NEXT: ret i8 [[TMP3]]
;
%3 = icmp eq i8 %1, %0
%4 = sub nsw i8 %0, %1
@@ -1480,10 +1474,8 @@
define <2 x i8> @select_sub_cmp_vec_swap(<2 x i8> %0, <2 x i8> %1) {
; CHECK-LABEL: @select_sub_cmp_vec_swap(
-; CHECK-NEXT: [[TMP3:%.*]] = icmp eq <2 x i8> [[TMP1:%.*]], [[TMP0:%.*]]
-; CHECK-NEXT: [[TMP4:%.*]] = sub nsw <2 x i8> [[TMP0]], [[TMP1]]
-; CHECK-NEXT: [[TMP5:%.*]] = select <2 x i1> [[TMP3]], <2 x i8> zeroinitializer, <2 x i8> [[TMP4]]
-; CHECK-NEXT: ret <2 x i8> [[TMP5]]
+; CHECK-NEXT: [[TMP3:%.*]] = sub nsw <2 x i8> [[TMP0:%.*]], [[TMP1:%.*]]
+; CHECK-NEXT: ret <2 x i8> [[TMP3]]
;
%3 = icmp eq <2 x i8> %1, %0
%4 = sub nsw <2 x i8> %0, %1
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4256,6 +4256,13 @@
NewOps[0] == NewOps[1])
return NewOps[0];
+ // x - x -> 0. This is non-refining, because x is non-poison by assumption
+ // and this case never wraps, so nowrap flags can be ignored.
+ if (Opcode == Instruction::Sub && NewOps[0] == NewOps[1]) {
+ assert(NewOps[0] == RepOp && "Precondition for non-poison assumption");
+ return Constant::getNullValue(I->getType());
+ }
+
// If we are substituting an absorber constant into a binop and extra
// poison can't leak if we remove the select -- because both operands of
// the binop are based on the same value -- then it may be safe to replace
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D150378.522537.patch
Type: text/x-patch
Size: 3334 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230516/6cccf69b/attachment.bin>
More information about the llvm-commits
mailing list