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[ValueTracking] update directlyImpliesPoison to look into select's condition 

This is a minor update in directlyImpliesPoison and makes it look into select's
condition.
Splitted from https://reviews.llvm.org/D96945
This commit is contained in:
Juneyoung Lee 2021-03-07 23:16:39 +09:00
parent cd938ab162
commit 2c16c4a43c
2 changed files with 6 additions and 4 deletions
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4
llvm/lib/Analysis/ValueTracking.cpp
View File

@ -4852,6 +4852,10 @@ static bool directlyImpliesPoison(const Value *ValAssumedPoison,
return directlyImpliesPoison(ValAssumedPoison, Op, Depth + 1);
});
// 'select ValAssumedPoison, _, _' is poison.
if (const auto *SI = dyn_cast<SelectInst>(I))
return directlyImpliesPoison(ValAssumedPoison, SI->getCondition(),
Depth + 1);
// V = extractvalue V0, idx
// V2 = extractvalue V0, idx2
// V0's elements are all poison or not. (e.g., add_with_overflow)

6
llvm/test/Transforms/InstCombine/select-safe-bool-transforms.ll
View File

@ -86,8 +86,7 @@ define i1 @merge_logical_and_and3(i1 %X, i1 %Y) {
define i1 @merge_two_logical_ands3(i1 %X, i1 %Y) {
; CHECK-LABEL: @merge_two_logical_ands3(
; CHECK-NEXT: [[C:%.*]] = select i1 [[X:%.*]], i1 [[Y:%.*]], i1 false
; CHECK-NEXT: [[RES:%.*]] = select i1 [[C]], i1 [[X]], i1 false
; CHECK-NEXT: ret i1 [[RES]]
; CHECK-NEXT: ret i1 [[C]]
;
%c = select i1 %X, i1 %Y, i1 false
%res = select i1 %c, i1 %X, i1 false
@ -223,8 +222,7 @@ define i1 @merge_logical_or_or3(i1 %X, i1 %Y) {
define i1 @merge_two_logical_ors3(i1 %X, i1 %Y) {
; CHECK-LABEL: @merge_two_logical_ors3(
; CHECK-NEXT: [[C:%.*]] = select i1 [[X:%.*]], i1 true, i1 [[Y:%.*]]
; CHECK-NEXT: [[RES:%.*]] = select i1 [[C]], i1 true, i1 [[X]]
; CHECK-NEXT: ret i1 [[RES]]
; CHECK-NEXT: ret i1 [[C]]
;
%c = select i1 %X, i1 true, i1 %Y
%res = select i1 %c, i1 true, i1 %X