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nodes when folding bitcasts of constants. We can't fold things and then check after-the-fact whether it was legal. Once we have formed the DAG node, arbitrary other nodes may have been collapsed to it. There is no easy way to go back. Instead, we need to test for the specific folding cases we're interested in and ensure those are legal first. This could in theory make this less powerful for bitcasting from an integer to some vector type, but AFAICT, that can't actually happen in the SDAG so its fine. Now, we *only* whitelist specific int->fp and fp->int bitcasts for post-legalization folding. I've added the test case from the PR. (Also as a note, this does not appear to be in 3.6, no backport needed) llvm-svn: 228656
36 lines
1.3 KiB
LLVM
36 lines
1.3 KiB
LLVM
; RUN: llc < %s | FileCheck %s
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-unknown"
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define void @PR22524({ float, float }* %arg) {
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; Check that we can materialize the zero constants we store in two places here,
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; and at least form a legal store of the floating point value at the end.
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; The DAG combiner at one point contained bugs that given enough permutations
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; would incorrectly form an illegal operation for the last of these stores when
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; it folded it to a zero too late to legalize the zero store operation. If this
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; ever starts forming a zero store instead of movss, the test case has stopped
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; being useful.
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;
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; CHECK-LABEL: PR22524:
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entry:
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%0 = getelementptr inbounds { float, float }* %arg, i32 0, i32 1
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store float 0.000000e+00, float* %0, align 4
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; CHECK: movl $0, 4(%rdi)
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%1 = getelementptr inbounds { float, float }* %arg, i64 0, i32 0
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%2 = bitcast float* %1 to i64*
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%3 = load i64* %2, align 8
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%4 = trunc i64 %3 to i32
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%5 = lshr i64 %3, 32
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%6 = trunc i64 %5 to i32
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%7 = bitcast i32 %6 to float
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%8 = fmul float %7, 0.000000e+00
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%9 = bitcast float* %1 to i32*
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store i32 %6, i32* %9, align 4
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; CHECK: movl $0, (%rdi)
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store float %8, float* %0, align 4
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; CHECK: movss %{{.*}}, 4(%rdi)
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ret void
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}
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