Index: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp =================================================================== --- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp +++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp @@ -322,6 +322,14 @@ 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!"); } Index: llvm/trunk/test/CodeGen/X86/pr41748.ll =================================================================== --- llvm/trunk/test/CodeGen/X86/pr41748.ll +++ llvm/trunk/test/CodeGen/X86/pr41748.ll @@ -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 +}