[PATCH] D153490: [RISCV] Properly handle partial writes in isConvertibleToVMV_V_V.

[Craig Topper via Phabricator via llvm-commits]

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We were only checking for the previous insructions to write exactly
the register or a super register. We ignored writes to a subregister
and continued searching for the producing instruction. We need to
abort instead.

There's another check inside the if body to abort if the registers
don't match exactly. So we just need to check for overlap so we
enter the if body.

The test is new and has not been commited yet.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D153490

Files:
  llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
  llvm/test/CodeGen/RISCV/rvv/vmv-copy.mir


Index: llvm/test/CodeGen/RISCV/rvv/vmv-copy.mir
===================================================================
--- llvm/test/CodeGen/RISCV/rvv/vmv-copy.mir
+++ llvm/test/CodeGen/RISCV/rvv/vmv-copy.mir
@@ -317,7 +317,7 @@
     ; CHECK-NEXT: $v10m2 = PseudoVLE16_V_M2 killed $x11, $noreg, 4 /* e16 */, implicit $vl, implicit $vtype
     ; CHECK-NEXT: $v10 = VMV1R_V $v8
     ; CHECK-NEXT: $v11 = VMV1R_V $v9
-    ; CHECK-NEXT: $v12m2 = PseudoVMV_V_V_M2 $v10m2, $noreg, 4 /* e16 */, implicit $vl, implicit $vtype
+    ; CHECK-NEXT: $v12m2 = VMV2R_V $v10m2
     $x0 = PseudoVSETVLI $x10, 201, implicit-def $vl, implicit-def $vtype
     $v10m2 = PseudoVLE16_V_M2 killed $x11, $noreg, 4, implicit $vl, implicit $vtype
     $v10 = COPY $v8
Index: llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
+++ llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
@@ -245,7 +245,7 @@
       for (const MachineOperand &MO : MBBI->explicit_operands()) {
         if (!MO.isReg() || !MO.isDef())
           continue;
-        if (!FoundDef && TRI->isSubRegisterEq(MO.getReg(), SrcReg)) {
+        if (!FoundDef && TRI->regsOverlap(MO.getReg(), SrcReg)) {
           // We only permit the source of COPY has the same LMUL as the defined
           // operand.
           // There are cases we need to keep the whole register copy if the LMUL


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