[ARM] Allow zext in ARMCodeGenPrepare

Treat zext instructions as roots, like we do for truncs.

Differential Revision: https://reviews.llvm.org/D50759

llvm-svn: 339868

llvm/lib/Target/ARM/ARMCodeGenPrepare.cpp

@@ -181,6 +181,8 @@ static bool isSink(Value *V) {
     return UsesNarrowValue(Return->getReturnValue());
   if (auto *Trunc = dyn_cast<TruncInst>(V))
     return UsesNarrowValue(Trunc->getOperand(0));
+  if (auto *ZExt = dyn_cast<ZExtInst>(V))
+    return UsesNarrowValue(ZExt->getOperand(0));
   if (auto *ICmp = dyn_cast<ICmpInst>(V))
     return ICmp->isSigned();
 
@@ -422,7 +424,8 @@ void IRPromoter::Mutate(Type *OrigTy,
     if (!isa<Instruction>(V) || !isa<IntegerType>(V->getType()))
       return nullptr;
 
-    if ((!Promoted.count(V) && !NewInsts.count(V)) || !TruncTysMap.count(V))
+    if ((!Promoted.count(V) && !NewInsts.count(V)) || !TruncTysMap.count(V) ||
+        Leaves.count(V))
       return nullptr;
 
     Type *TruncTy = TruncTysMap[V];
@@ -463,7 +466,7 @@ void IRPromoter::Mutate(Type *OrigTy,
       }
     }
   }
-  LLVM_DEBUG(dbgs() << "ARM CGP: Mutation complete.\n");
+  LLVM_DEBUG(dbgs() << "ARM CGP: Mutation complete:\n");
 }
 
 /// We accept most instructions, as well as Arguments and ConstantInsts. We
@@ -492,10 +495,12 @@ bool ARMCodeGenPrepare::isSupportedValue(Value *V) {
       isa<LoadInst>(V))
     return isSupportedType(V);
 
-  // Currently, Trunc is the only cast we support.
   if (auto *Trunc = dyn_cast<TruncInst>(V))
     return isSupportedType(Trunc->getOperand(0));
 
+  if (auto *ZExt = dyn_cast<ZExtInst>(V))
+    return isSupportedType(ZExt->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
   // still be roots.

llvm/test/CodeGen/ARM/arm-cgp-calls.ll

@@ -42,7 +42,7 @@ define i16 @promote_i8_sink_i16_1(i8 zeroext %arg0, i16 zeroext %arg1, i16 zeroe
 ; CHECK-COMMON-LABEL: promote_i8_sink_i16_2
 ; CHECK-COMMON: bl dummy_i8
 ; CHECK-COMMON: adds r0, #1
-; CHECK-COMMON: uxtb r0, r0
+; CHECK-COMMON-NOT: uxt
 ; CHECK-COMMON: cmp r0
 define i16 @promote_i8_sink_i16_2(i8 zeroext %arg0, i8 zeroext %arg1, i16 zeroext %arg2) {
   %call = tail call zeroext i8 @dummy_i8(i8 %arg0)

llvm/test/CodeGen/ARM/arm-cgp-zext-truncs.ll

@@ -51,12 +51,12 @@ entry:
   ret i8 %4
 }
 
-; The pass will bail because of the zext, otherwise we'd want something like:
-; ldrb [[LD:r[^ ]+]], [r0]
-; subs [[SUB:r[^ ]+]], [[LD]], #1
-; cmp [[LD]], [[SUB]]
+; The pass perform the transform, but a uxtb will still be inserted to handle
+; the zext to the icmp.
 ; CHECK-COMMON-LABEL: icmp_i32_zext:
+; CHECK-COMMON: sub
 ; CHECK-COMMON: uxtb
+; CHECK-COMMON: cmp
 define i8 @icmp_i32_zext(i8* %ptr) {
 entry:
   %gep = getelementptr inbounds i8, i8* %ptr, i32 0
@@ -85,8 +85,10 @@ exit:
   ret i8 %2
 }
 
-; Won't handle zext or sext
+; Won't don't handle sext
 ; CHECK-COMMON-LABEL: icmp_sext_zext_store_i8_i16
+; CHECK-COMMON: ldrb
+; CHECK-COMMON: ldrsh
 define i32 @icmp_sext_zext_store_i8_i16() {
 entry:
   %0 = load i8, i8* getelementptr inbounds ([16 x i8], [16 x i8]* @d_uch, i32 0, i32 2), align 1
@@ -100,12 +102,13 @@ entry:
   ret i32 %conv3
 }
 
-; Pass will bail because of the zext, otherwise:
-; ldrb [[LD:r[^ ]+]], [r1]
-; subs [[SUB:r[^ ]+]], #1
-; cmp [[SUB]], #3
 ; CHECK-COMMON-LABEL: or_icmp_ugt:
-; CHECK-COMMON: uxt
+; CHECK-COMMON:     ldrb
+; CHECK-COMMON:     sub.w
+; CHECK-COMMON-NOT: uxt
+; CHECK-COMMON:     cmp.w
+; CHECK-COMMON-NOT: uxt
+; CHECK-COMMON:     cmp
 define i1 @or_icmp_ugt(i32 %arg, i8* %ptr) {
 entry:
   %0 = load i8, i8* %ptr
@@ -149,9 +152,12 @@ exit:
   ret i16 %res
 }
 
-; Pass will bail because of the zext
+; We currently only handle truncs as sinks, so a uxt will still be needed for
+; the icmp ugt instruction.
 ; CHECK-COMMON-LABEL: urem_trunc_icmps
+; CHECK-COMMON: cmp
 ; CHECK-COMMON: uxt
+; CHECK-COMMON: cmp
 define void @urem_trunc_icmps(i16** %in, i32* %g, i32* %k) {
 entry:
   %ptr = load i16*, i16** %in, align 4
@@ -223,7 +229,6 @@ exit:
   ret void
 }
 
-; Again, zexts will prevent the transform.
 ; Check that %exp requires uxth in all cases, and will also be required to
 ; promote %1 for the call - unless we can generate a uadd16.
 ; CHECK-COMMON-LABEL: zext_load_sink_call: