[AArch64] Enable aggressivelyPreferBuildVectorSources (llvm#142729)

This helps to remove some inefficient buildvector lowering by converting
extract_vector_elt(buildvector) to the original source.

Author: davemgreen

llvm/lib/Target/AArch64/AArch64ISelLowering.h

@@ -449,6 +449,10 @@ class AArch64TargetLowering : public TargetLowering {
   /// Enable aggressive FMA fusion on targets that want it.
   bool enableAggressiveFMAFusion(EVT VT) const override;
 
+  bool aggressivelyPreferBuildVectorSources(EVT VecVT) const override {
+    return true;
+  }
+
   /// Returns the size of the platform's va_list object.
   unsigned getVaListSizeInBits(const DataLayout &DL) const override;
 

llvm/test/CodeGen/AArch64/GlobalISel/combine-build-vector.mir

@@ -55,13 +55,9 @@ body:             |
     ; CHECK-NEXT: {{  $}}
     ; CHECK-NEXT: %arg1:_(s64) = COPY $x0
     ; CHECK-NEXT: %arg2:_(s64) = COPY $x1
-    ; CHECK-NEXT: %zero:_(s64) = G_CONSTANT i64 0
-    ; CHECK-NEXT: %one:_(s64) = G_CONSTANT i64 1
     ; CHECK-NEXT: %bv:_(<2 x s64>) = G_BUILD_VECTOR %arg1(s64), %arg2(s64)
-    ; CHECK-NEXT: %extract:_(s64) = G_EXTRACT_VECTOR_ELT %bv(<2 x s64>), %zero(s64)
-    ; CHECK-NEXT: %extract2:_(s64) = G_EXTRACT_VECTOR_ELT %bv(<2 x s64>), %one(s64)
-    ; CHECK-NEXT: $x0 = COPY %extract(s64)
-    ; CHECK-NEXT: $x1 = COPY %extract2(s64)
+    ; CHECK-NEXT: $x0 = COPY %arg1(s64)
+    ; CHECK-NEXT: $x1 = COPY %arg2(s64)
     ; CHECK-NEXT: $q0 = COPY %bv(<2 x s64>)
     ; CHECK-NEXT: RET_ReallyLR implicit $x0
     %arg1:_(s64) = COPY $x0

llvm/test/CodeGen/AArch64/GlobalISel/combine-extract-vec-elt.mir

@@ -175,10 +175,8 @@ body:             |
     ; CHECK-NEXT: {{  $}}
     ; CHECK-NEXT: %arg1:_(s64) = COPY $x0
     ; CHECK-NEXT: %arg2:_(s64) = COPY $x1
-    ; CHECK-NEXT: %zero:_(s64) = G_CONSTANT i64 0
     ; CHECK-NEXT: %bv:_(<2 x s64>) = G_BUILD_VECTOR %arg1(s64), %arg2(s64)
-    ; CHECK-NEXT: %extract:_(s64) = G_EXTRACT_VECTOR_ELT %bv(<2 x s64>), %zero(s64)
-    ; CHECK-NEXT: $x0 = COPY %extract(s64)
+    ; CHECK-NEXT: $x0 = COPY %arg1(s64)
     ; CHECK-NEXT: $q0 = COPY %bv(<2 x s64>)
     ; CHECK-NEXT: RET_ReallyLR implicit $x0
     %arg1:_(s64) = COPY $x0

llvm/test/CodeGen/AArch64/GlobalISel/combine-insert-vec-elt.mir

@@ -278,8 +278,8 @@ body:             |
     ; CHECK: liveins: $x0
     ; CHECK-NEXT: {{  $}}
     ; CHECK-NEXT: [[C:%[0-9]+]]:_(s8) = G_CONSTANT i8 127
-    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(p0) = COPY $x0
     ; CHECK-NEXT: [[BUILD_VECTOR:%[0-9]+]]:_(<32 x s8>) = G_BUILD_VECTOR [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8)
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(p0) = COPY $x0
     ; CHECK-NEXT: G_STORE [[BUILD_VECTOR]](<32 x s8>), [[COPY]](p0) :: (store (<32 x s8>))
     ; CHECK-NEXT: RET_ReallyLR
     %3:_(s8) = G_CONSTANT i8 127