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llvm-mirror/test/Transforms/InstCombine/umulo.ll
Philip Reames bfe000bb38 [instcombine] Fold overflow check using umulo to comparison
If we have a umul.with.overflow where the multiply result is not used and one of the operands is a constant, we can perform the overflow check cheaper with a comparison then by performing the multiply and extracting the overflow flag.

(Noticed when looking at the conditions SCEV emits for overflow checks.)

Differential Revision: https://reviews.llvm.org/D104665
2021-06-25 10:25:45 -07:00

97 lines
2.9 KiB
LLVM

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S | FileCheck %s
declare { i64, i1 } @llvm.umul.with.overflow.i64(i64, i64)
declare { i8, i1 } @llvm.umul.with.overflow.i8(i8, i8)
define i1 @test_generic(i64 %a, i64 %b) {
; CHECK-LABEL: @test_generic(
; CHECK-NEXT: [[RES:%.*]] = tail call { i64, i1 } @llvm.umul.with.overflow.i64(i64 [[A:%.*]], i64 [[B:%.*]])
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i64, i1 } [[RES]], 1
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i64, i1 } @llvm.umul.with.overflow.i64(i64 %a, i64 %b)
%overflow = extractvalue { i64, i1 } %res, 1
ret i1 %overflow
}
define i1 @test_constant0(i8 %a) {
; CHECK-LABEL: @test_constant0(
; CHECK-NEXT: ret i1 false
;
%res = tail call { i8, i1 } @llvm.umul.with.overflow.i8(i8 %a, i8 0)
%overflow = extractvalue { i8, i1 } %res, 1
ret i1 %overflow
}
define i1 @test_constant1(i8 %a) {
; CHECK-LABEL: @test_constant1(
; CHECK-NEXT: ret i1 false
;
%res = tail call { i8, i1 } @llvm.umul.with.overflow.i8(i8 %a, i8 1)
%overflow = extractvalue { i8, i1 } %res, 1
ret i1 %overflow
}
define i1 @test_constant2(i8 %a) {
; CHECK-LABEL: @test_constant2(
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp slt i8 [[A:%.*]], 0
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.umul.with.overflow.i8(i8 %a, i8 2)
%overflow = extractvalue { i8, i1 } %res, 1
ret i1 %overflow
}
define i1 @test_constant3(i8 %a) {
; CHECK-LABEL: @test_constant3(
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ugt i8 [[A:%.*]], 85
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.umul.with.overflow.i8(i8 %a, i8 3)
%overflow = extractvalue { i8, i1 } %res, 1
ret i1 %overflow
}
define i1 @test_constant4(i8 %a) {
; CHECK-LABEL: @test_constant4(
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ugt i8 [[A:%.*]], 63
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.umul.with.overflow.i8(i8 %a, i8 4)
%overflow = extractvalue { i8, i1 } %res, 1
ret i1 %overflow
}
define i1 @test_constant127(i8 %a) {
; CHECK-LABEL: @test_constant127(
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ugt i8 [[A:%.*]], 2
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.umul.with.overflow.i8(i8 %a, i8 127)
%overflow = extractvalue { i8, i1 } %res, 1
ret i1 %overflow
}
define i1 @test_constant128(i8 %a) {
; CHECK-LABEL: @test_constant128(
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ugt i8 [[A:%.*]], 1
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.umul.with.overflow.i8(i8 %a, i8 128)
%overflow = extractvalue { i8, i1 } %res, 1
ret i1 %overflow
}
define i1 @test_constant255(i8 %a) {
; CHECK-LABEL: @test_constant255(
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ugt i8 [[A:%.*]], 1
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.umul.with.overflow.i8(i8 %a, i8 255)
%overflow = extractvalue { i8, i1 } %res, 1
ret i1 %overflow
}