[llvm-dev] Bug 20871 -- is there a fix or work around?

[Riyaz Puthiyapurayil via llvm-dev]

Ignore the suggested fix in my earlier post. How about this?

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 20c81c3..b8ebf42 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1632,10 +1632,11 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
   if (!Subtarget.is64Bit()) {
     // These libcalls are not available in 32-bit.
     setLibcallName(RTLIB::SHL_I128, nullptr);
     setLibcallName(RTLIB::SRL_I128, nullptr);
     setLibcallName(RTLIB::SRA_I128, nullptr);
+    setLibcallName(RTLIB::MUL_I128, nullptr);
   }
   // Combine sin / cos into one node or libcall if possible.
   if (Subtarget.hasSinCos()) {
     setLibcallName(RTLIB::SINCOS_F32, "sincosf");

This will make the Legalizer choose the brute force approach below:

void DAGTypeLegalizer::ExpandIntRes_MUL(SDNode *N,
                                        SDValue &Lo, SDValue &Hi) {
...

  if (LC == RTLIB::UNKNOWN_LIBCALL || !TLI.getLibcallName(LC)) {
    // We'll expand the multiplication by brute force because we have no other
    // options. This is a trivially-generalized version of the code from
    // Hacker's Delight (itself derived from Knuth's Algorithm M from section
    // 4.3.1).
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