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[SelectionDAG][X86] Support inline assembly returning an mmx register into a type with fewer than 64 bits.

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It's possible to use the 'y' mmx constraint with a type narrower than 64-bits.

This patch supports this by bitcasting the mmx type to 64-bits and then
truncating to the desired type.

There are probably other missing type combinations we need to support, but this
is the case we have a bug report for.

Fixes PR41748.

Differential Revision: https://reviews.llvm.org/D61582

llvm-svn: 360069
This commit is contained in:
Craig Topper 2019-05-06 19:50:14 +00:00
parent 79073a3227
commit c804c11acc
2 changed files with 23 additions and 0 deletions
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8
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
View File

@ -322,6 +322,14 @@ static SDValue getCopyFromParts(SelectionDAG &DAG, const SDLoc &DL,
return DAG.getNode(ISD::FP_EXTEND, DL, ValueVT, Val);
}
// Handle MMX to a narrower integer type by bitcasting MMX to integer and
// then truncating.
if (PartEVT == MVT::x86mmx && ValueVT.isInteger() &&
ValueVT.bitsLT(PartEVT)) {
Val = DAG.getNode(ISD::BITCAST, DL, MVT::i64, Val);
return DAG.getNode(ISD::TRUNCATE, DL, ValueVT, Val);
}
report_fatal_error("Unknown mismatch in getCopyFromParts!");
}

15
test/CodeGen/X86/pr41748.ll Normal file
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@ -0,0 +1,15 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=x86_64-apple-macosx10.14.0 -mattr=mmx | FileCheck %s
define i32 @foo(i32 %a) {
; CHECK-LABEL: foo:
; CHECK: ## %bb.0: ## %entry
; CHECK-NEXT: ## InlineAsm Start
; CHECK-NEXT: movd %edi, %mm0
; CHECK-NEXT: ## InlineAsm End
; CHECK-NEXT: movd %mm0, %eax
; CHECK-NEXT: retq
entry:
%0 = tail call i32 asm sideeffect "movd $1, $0", "=y,r,~{dirflag},~{fpsr},~{flags}"(i32 %a)
ret i32 %0
}