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3e2b1fd515
This should bring signed div/rem analysis up to the same level as unsigned. We use icmp simplification to determine when the divisor is known greater than the dividend. Each positive test is followed by a negative test to show that we're not overstepping the boundaries of the known bits. There are extra tests for the signed-min-value special cases. Alive proofs: http://rise4fun.com/Alive/WI5 Differential Revision: https://reviews.llvm.org/D37713 llvm-svn: 313264
70 lines
1.2 KiB
LLVM
70 lines
1.2 KiB
LLVM
; RUN: opt < %s -instsimplify -S | FileCheck %s
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; PR8862
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define i32 @shift1(i32 %A, i32 %B) {
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; CHECK-LABEL: @shift1(
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; CHECK-NEXT: ret i32 %A
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;
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%C = lshr exact i32 %A, %B
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%D = shl nuw i32 %C, %B
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ret i32 %D
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}
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define i32 @shift2(i32 %A, i32 %B) {
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; CHECK-LABEL: @shift2(
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; CHECK-NEXT: [[C:%.*]] = lshr i32 %A, %B
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; CHECK-NEXT: [[D:%.*]] = shl nuw i32 [[C]], %B
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; CHECK-NEXT: ret i32 [[D]]
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;
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%C = lshr i32 %A, %B
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%D = shl nuw i32 %C, %B
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ret i32 %D
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}
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define i32 @shift3(i32 %A, i32 %B) {
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; CHECK-LABEL: @shift3(
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; CHECK-NEXT: ret i32 %A
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;
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%C = ashr exact i32 %A, %B
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%D = shl nuw i32 %C, %B
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ret i32 %D
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}
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define i32 @shift4(i32 %A, i32 %B) {
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; CHECK-LABEL: @shift4(
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; CHECK-NEXT: ret i32 %A
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;
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%C = shl nuw i32 %A, %B
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%D = lshr i32 %C, %B
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ret i32 %D
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}
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define i32 @shift5(i32 %A, i32 %B) {
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; CHECK-LABEL: @shift5(
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; CHECK-NEXT: ret i32 %A
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;
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%C = shl nsw i32 %A, %B
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%D = ashr i32 %C, %B
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ret i32 %D
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}
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define i32 @div1(i32 %V) {
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; CHECK-LABEL: @div1(
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; CHECK-NEXT: ret i32 0
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;
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%A = udiv i32 %V, -2147483648
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%B = udiv i32 %A, -2147483648
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ret i32 %B
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}
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define i32 @div2(i32 %V) {
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; CHECK-LABEL: @div2(
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; CHECK-NEXT: ret i32 0
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;
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%A = sdiv i32 %V, -1
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%B = sdiv i32 %A, -2147483648
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ret i32 %B
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}
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