[ARM] Allow bitcasts in ARMCodeGenPrepare

Allow bitcasts in the use-def chains, treating them as sources.

Differential Revision: https://reviews.llvm.org/D50758

llvm-svn: 342032

2 files changed, 48 insertions, 5 deletions

diff --git a/llvm/lib/Target/ARM/ARMCodeGenPrepare.cpp b/llvm/lib/Target/ARM/ARMCodeGenPrepare.cpp
index f7df39ac385..bc33e65b067 100644
--- a/llvm/lib/Target/ARM/ARMCodeGenPrepare.cpp
+++ b/llvm/lib/Target/ARM/ARMCodeGenPrepare.cpp
@@ -209,6 +209,8 @@ static bool isSource(Value *V) {
     return true;
   else if (isa<LoadInst>(V))
     return true;
+  else if (isa<BitCastInst>(V))
+    return true;
   else if (auto *Call = dyn_cast<CallInst>(V))
     return Call->hasRetAttr(Attribute::AttrKind::ZExt);
   return false;
@@ -545,11 +547,8 @@ bool ARMCodeGenPrepare::isSupportedValue(Value *V) {
       isa<LoadInst>(V))
     return isSupportedType(V);
 
-  if (auto *Trunc = dyn_cast<TruncInst>(V))
-    return isSupportedType(Trunc->getOperand(0));
-
-  if (auto *ZExt = dyn_cast<ZExtInst>(V))
-    return isSupportedType(ZExt->getOperand(0));
+  if (isa<CastInst>(V) && !isa<SExtInst>(V)) 
+    return isSupportedType(cast<CastInst>(V)->getOperand(0));
 
   // Special cases for calls as we need to check for zeroext
   // TODO We should accept calls even if they don't have zeroext, as they can
diff --git a/llvm/test/CodeGen/ARM/arm-cgp-zext-truncs.ll b/llvm/test/CodeGen/ARM/arm-cgp-casts.ll
index 021b11f4f2d..e742ed7dba2 100644
--- a/llvm/test/CodeGen/ARM/arm-cgp-zext-truncs.ll
+++ b/llvm/test/CodeGen/ARM/arm-cgp-casts.ll
@@ -288,6 +288,50 @@ cleanup:
   ret i32 %retval.0
 }
 
+; CHECK-COMMON-LABEL: bitcast_i16
+; CHECK-COMMON-NOT: uxt
+define i16 @bitcast_i16(i16 zeroext %arg0, i16 zeroext %arg1) {
+entry:
+  %cast = bitcast i16 12345 to i16
+  %add = add nuw i16 %arg0, 1
+  %cmp = icmp ule i16 %add, %cast
+  %res = select i1 %cmp, i16 %arg1, i16 32657
+  ret i16 %res
+}
+
+; CHECK-COMMON-LABEL: bitcast_i8
+; CHECK-COMMON-NOT: uxt
+define i8 @bitcast_i8(i8 zeroext %arg0, i8 zeroext %arg1) {
+entry:
+  %cast = bitcast i8 127 to i8
+  %mul = shl nuw i8 %arg0, 1
+  %cmp = icmp uge i8 %mul, %arg1
+  %res = select i1 %cmp, i8 %cast, i8 128
+  ret i8 %res
+}
+
+; CHECK-COMMON-LABEL: bitcast_i16_minus
+; CHECK-COMMON-NOT: uxt
+define i16 @bitcast_i16_minus(i16 zeroext %arg0, i16 zeroext %arg1) {
+entry:
+  %cast = bitcast i16 -12345 to i16
+  %xor = xor i16 %arg0, 7
+  %cmp = icmp eq i16 %xor, %arg1
+  %res = select i1 %cmp, i16 %cast, i16 32657
+  ret i16 %res
+}
+
+; CHECK-COMMON-LABEL: bitcast_i8_minus
+; CHECK-COMMON-NOT: uxt
+define i8 @bitcast_i8_minus(i8 zeroext %arg0, i8 zeroext %arg1) {
+entry:
+  %cast = bitcast i8 -127 to i8
+  %and = and i8 %arg0, 3
+  %cmp = icmp ne i8 %and, %arg1
+  %res = select i1 %cmp, i8 %cast, i8 128
+  ret i8 %res
+}
+
 declare %class.x* @_ZNK2ae2afEv(%class.ae*) local_unnamed_addr
 declare %class.v* @_ZN1x2acEv(%class.x*) local_unnamed_addr
 declare i32 @dummy(i32, i32)