[AArch64][GlobalISel] Unmerge into scalars from a vector should use FPR bank.

This currently shows up as a selection fallback since the dest regs were given
GPR banks but the source was a vector FPR reg.

Differential Revision: https://reviews.llvm.org/D57408

llvm-svn: 352545

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64RegisterBankInfo.cpp b/llvm/lib/Target/AArch64/AArch64RegisterBankInfo.cpp
index bbf4e4e0571..23d7e18436d 100644
--- a/llvm/lib/Target/AArch64/AArch64RegisterBankInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64RegisterBankInfo.cpp
@@ -669,7 +669,11 @@ AArch64RegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
              &AArch64::FPRRegBank;
     };
 
-    if (any_of(MRI.use_instructions(MI.getOperand(0).getReg()),
+    LLT SrcTy = MRI.getType(MI.getOperand(MI.getNumOperands()-1).getReg());
+    // UNMERGE into scalars from a vector should always use FPR.
+    // Likewise if any of the uses are FP instructions.
+    if (SrcTy.isVector() ||
+        any_of(MRI.use_instructions(MI.getOperand(0).getReg()),
                [&](MachineInstr &MI) { return HasFPConstraints(MI); })) {
       // Set the register bank of every operand to FPR.
       for (unsigned Idx = 0, NumOperands = MI.getNumOperands();