f7d1baa414
For always poison shifts, any KnownBits return value is valid. Currently we return unknown, but returning zero is generally more profitable. We had some code in ValueTracking that tried to do this, but was actually dead code. Differential Revision: https://reviews.llvm.org/D150648
72 lines
2.5 KiB
LLVM
72 lines
2.5 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
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; RUN: opt < %s --data-layout="e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" -S -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck %s
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; RUN: opt < %s --data-layout="e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128" -S -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck %s
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; In general, we can't deal with ashr.
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define i32 @t0(i32 %x, i32 %y) {
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; CHECK-LABEL: 't0'
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; CHECK-NEXT: Classifying expressions for: @t0
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; CHECK-NEXT: %i0 = ashr i32 %x, %y
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; CHECK-NEXT: --> %i0 U: full-set S: full-set
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; CHECK-NEXT: Determining loop execution counts for: @t0
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;
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%i0 = ashr i32 %x, %y
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ret i32 %i0
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}
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; Not even if we know it's exact
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define i32 @t1(i32 %x, i32 %y) {
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; CHECK-LABEL: 't1'
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; CHECK-NEXT: Classifying expressions for: @t1
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; CHECK-NEXT: %i0 = ashr exact i32 %x, %y
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; CHECK-NEXT: --> %i0 U: full-set S: full-set
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; CHECK-NEXT: Determining loop execution counts for: @t1
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;
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%i0 = ashr exact i32 %x, %y
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ret i32 %i0
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}
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; Not even if the shift amount is a constant.
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define i32 @t2(i32 %x, i32 %y) {
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; CHECK-LABEL: 't2'
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; CHECK-NEXT: Classifying expressions for: @t2
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; CHECK-NEXT: %i0 = ashr i32 %x, 4
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; CHECK-NEXT: --> %i0 U: [-134217728,134217728) S: [-134217728,134217728)
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; CHECK-NEXT: Determining loop execution counts for: @t2
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;
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%i0 = ashr i32 %x, 4
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ret i32 %i0
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}
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; However, if it's a constant AND the shift is exact, we can model it!
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define i32 @t3(i32 %x, i32 %y) {
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; CHECK-LABEL: 't3'
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; CHECK-NEXT: Classifying expressions for: @t3
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; CHECK-NEXT: %i0 = ashr exact i32 %x, 4
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; CHECK-NEXT: --> %i0 U: [-134217728,134217728) S: [-134217728,134217728)
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; CHECK-NEXT: Determining loop execution counts for: @t3
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;
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%i0 = ashr exact i32 %x, 4
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ret i32 %i0
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}
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; As long as the shift amount is in-bounds
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define i32 @t4(i32 %x, i32 %y) {
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; CHECK-LABEL: 't4'
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; CHECK-NEXT: Classifying expressions for: @t4
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; CHECK-NEXT: %i0 = ashr exact i32 %x, 32
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; CHECK-NEXT: --> %i0 U: [0,1) S: [0,1)
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; CHECK-NEXT: Determining loop execution counts for: @t4
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;
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%i0 = ashr exact i32 %x, 32
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ret i32 %i0
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}
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; One more test, just to see that we model constant correctly
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define i32 @t5(i32 %x, i32 %y) {
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; CHECK-LABEL: 't5'
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; CHECK-NEXT: Classifying expressions for: @t5
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; CHECK-NEXT: %i0 = ashr exact i32 %x, 5
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; CHECK-NEXT: --> %i0 U: [-67108864,67108864) S: [-67108864,67108864)
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; CHECK-NEXT: Determining loop execution counts for: @t5
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;
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%i0 = ashr exact i32 %x, 5
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ret i32 %i0
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}
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