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[InstCombine] Fold uadd.sat(a, b) == 0 and usub.sat(a, b) == 0

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This adds folds for comparing uadd.sat/usub.sat with zero:

 * uadd.sat(a, b) == 0 => a == 0 && b == 0 => (a | b) == 0
 * usub.sat(a, b) == 0 => a <= b

And inverted forms for !=.

Differential Revision: https://reviews.llvm.org/D69224

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@375374 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nikita Popov
2019-10-20 20:19:42 +00:00
parent 2b0c82a99f
commit e568120da3
2 changed files with 30 additions and 10 deletions
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test/Transforms/InstCombine/saturating-add-sub.ll
+8 -10
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@@ -1158,9 +1158,9 @@ define i8 @test_scalar_uadd_sub_const(i8 %a) {
define i1 @scalar_uadd_eq_zero(i8 %a, i8 %b) {
; CHECK-LABEL: @scalar_uadd_eq_zero(
; CHECK-NEXT: [[SAT:%.*]] = call i8 @llvm.uadd.sat.i8(i8 [[A:%.*]], i8 [[B:%.*]])
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[SAT]], 0
; CHECK-NEXT: ret i1 [[CMP]]
; CHECK-NEXT: [[TMP1:%.*]] = or i8 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i8 [[TMP1]], 0
; CHECK-NEXT: ret i1 [[TMP2]]
;
%sat = call i8 @llvm.uadd.sat.i8(i8 %a, i8 %b)
%cmp = icmp eq i8 %sat, 0
@@ -1169,9 +1169,9 @@ define i1 @scalar_uadd_eq_zero(i8 %a, i8 %b) {
define i1 @scalar_uadd_ne_zero(i8 %a, i8 %b) {
; CHECK-LABEL: @scalar_uadd_ne_zero(
; CHECK-NEXT: [[SAT:%.*]] = call i8 @llvm.uadd.sat.i8(i8 [[A:%.*]], i8 [[B:%.*]])
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i8 [[SAT]], 0
; CHECK-NEXT: ret i1 [[CMP]]
; CHECK-NEXT: [[TMP1:%.*]] = or i8 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp ne i8 [[TMP1]], 0
; CHECK-NEXT: ret i1 [[TMP2]]
;
%sat = call i8 @llvm.uadd.sat.i8(i8 %a, i8 %b)
%cmp = icmp ne i8 %sat, 0
@@ -1180,8 +1180,7 @@ define i1 @scalar_uadd_ne_zero(i8 %a, i8 %b) {
define i1 @scalar_usub_eq_zero(i8 %a, i8 %b) {
; CHECK-LABEL: @scalar_usub_eq_zero(
; CHECK-NEXT: [[SAT:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[A:%.*]], i8 [[B:%.*]])
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[SAT]], 0
; CHECK-NEXT: [[CMP:%.*]] = icmp ule i8 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%sat = call i8 @llvm.usub.sat.i8(i8 %a, i8 %b)
@@ -1191,8 +1190,7 @@ define i1 @scalar_usub_eq_zero(i8 %a, i8 %b) {
define i1 @scalar_usub_ne_zero(i8 %a, i8 %b) {
; CHECK-LABEL: @scalar_usub_ne_zero(
; CHECK-NEXT: [[SAT:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[A:%.*]], i8 [[B:%.*]])
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i8 [[SAT]], 0
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%sat = call i8 @llvm.usub.sat.i8(i8 %a, i8 %b)