[ARM] Add some VCMP folding and canonicalisation

The VCMP instructions in MVE can accept a register or ZR, but only as
the right hand operator. Most of the time this will already be correct
because the icmp will have been canonicalised that way already. There
are some cases in the lowering of float conditions that this will not
apply to though. This code should fix up those cases.

Differential Revision: https://reviews.llvm.org/D70822

1 files changed, 19 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/Utils/ARMBaseInfo.h b/llvm/lib/Target/ARM/Utils/ARMBaseInfo.h
index aa3aca359cb..11cb1a162e2 100644
--- a/llvm/lib/Target/ARM/Utils/ARMBaseInfo.h
+++ b/llvm/lib/Target/ARM/Utils/ARMBaseInfo.h
@@ -64,6 +64,25 @@ inline static CondCodes getOppositeCondition(CondCodes CC) {
   case LE: return GT;
   }
 }
+
+/// getSwappedCondition - assume the flags are set by MI(a,b), return
+/// the condition code if we modify the instructions such that flags are
+/// set by MI(b,a).
+inline static ARMCC::CondCodes getSwappedCondition(ARMCC::CondCodes CC) {
+  switch (CC) {
+  default: return ARMCC::AL;
+  case ARMCC::EQ: return ARMCC::EQ;
+  case ARMCC::NE: return ARMCC::NE;
+  case ARMCC::HS: return ARMCC::LS;
+  case ARMCC::LO: return ARMCC::HI;
+  case ARMCC::HI: return ARMCC::LO;
+  case ARMCC::LS: return ARMCC::HS;
+  case ARMCC::GE: return ARMCC::LE;
+  case ARMCC::LT: return ARMCC::GT;
+  case ARMCC::GT: return ARMCC::LT;
+  case ARMCC::LE: return ARMCC::GE;
+  }
+}
 } // end namespace ARMCC
 
 namespace ARMVCC {