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aff7184247
Summary:
Specifically, we transform
zext(2^K * (trunc X to iN)) to iM ->
2^K * (zext(trunc X to i{N-K}) to iM)<nuw>
This is helpful because pulling the 2^K out of the zext allows further
optimizations.
Reviewers: sanjoy
Subscribers: hiraditya, llvm-commits, timshen
Differential Revision: https://reviews.llvm.org/D48158
llvm-svn: 334737
42 lines
990 B
LLVM
42 lines
990 B
LLVM
; RUN: opt < %s -scalar-evolution -analyze | FileCheck %s
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; CHECK-LABEL: @test1
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; CHECK: --> (zext
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; CHECK: --> (zext
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; CHECK-NOT: --> (zext
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define i32 @test1(i32 %x) {
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%n = and i32 %x, 255
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%y = xor i32 %n, 255
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ret i32 %y
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}
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; ScalarEvolution shouldn't try to analyze %z into something like
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; --> (zext i4 (-1 + (-1 * (trunc i64 (8 * %x) to i4))) to i64)
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; or
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; --> (8 * (zext i1 (trunc i64 ((8 * %x) /u 8) to i1) to i64))
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; CHECK-LABEL: @test2
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; CHECK: --> (8 * (zext i1 (trunc i64 %x to i1) to i64))
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define i64 @test2(i64 %x) {
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%a = shl i64 %x, 3
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%t = and i64 %a, 8
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%z = xor i64 %t, 8
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ret i64 %z
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}
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; Check that we transform the naive lowering of the sequence below,
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; (4 * (zext i5 (2 * (trunc i32 %x to i5)) to i32)),
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; to
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; (8 * (zext i4 (trunc i32 %x to i4) to i32))
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;
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; CHECK-LABEL: @test3
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define i32 @test3(i32 %x) {
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%a = mul i32 %x, 8
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; CHECK: %b
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; CHECK-NEXT: --> (8 * (zext i4 (trunc i32 %x to i4) to i32))
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%b = and i32 %a, 124
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ret i32 %b
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}
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