[GlobalISel] Translate scalar sequential vecreduce.fadd/fmul as fadd/fmul. (#153966)

A llvm.vector.reduce.fadd(float, <1 x float>) will be translated to
G_VECREDUCE_SEQ_FADD with two scalar operands, which is illegal
according to the verifier. This makes sure we generate a fadd/fmul
instead.

Author: davemgreen

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

@@ -2522,6 +2522,9 @@ bool IRTranslator::translateKnownIntrinsic(const CallInst &CI, Intrinsic::ID ID,
       Opc = ID == Intrinsic::vector_reduce_fadd
                 ? TargetOpcode::G_VECREDUCE_SEQ_FADD
                 : TargetOpcode::G_VECREDUCE_SEQ_FMUL;
+      if (!MRI->getType(VecSrc).isVector())
+        Opc = ID == Intrinsic::vector_reduce_fadd ? TargetOpcode::G_FADD
+                                                  : TargetOpcode::G_FMUL;
       MIRBuilder.buildInstr(Opc, {Dst}, {ScalarSrc, VecSrc},
                             MachineInstr::copyFlagsFromInstruction(CI));
       return true;

llvm/test/CodeGen/AArch64/GlobalISel/irtranslator-reductions.ll

@@ -16,6 +16,21 @@ define float @fadd_seq(float %start, <4 x float> %vec) {
   ret float %res
 }
 
+define float @fadd_seq_scalar(float %start, <1 x float> %vec) {
+  ; CHECK-LABEL: name: fadd_seq_scalar
+  ; CHECK: bb.1 (%ir-block.0):
+  ; CHECK-NEXT:   liveins: $d1, $s0
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[COPY:%[0-9]+]]:_(s32) = COPY $s0
+  ; CHECK-NEXT:   [[COPY1:%[0-9]+]]:_(<2 x s32>) = COPY $d1
+  ; CHECK-NEXT:   [[UV:%[0-9]+]]:_(s32), [[UV1:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[COPY1]](<2 x s32>)
+  ; CHECK-NEXT:   [[FADD:%[0-9]+]]:_(s32) = G_FADD [[COPY]], [[UV]]
+  ; CHECK-NEXT:   $s0 = COPY [[FADD]](s32)
+  ; CHECK-NEXT:   RET_ReallyLR implicit $s0
+  %res = call float @llvm.vector.reduce.fadd.v1f32(float %start, <1 x float> %vec)
+  ret float %res
+}
+
 define float @fadd_fast(float %start, <4 x float> %vec) {
   ; CHECK-LABEL: name: fadd_fast
   ; CHECK: bb.1 (%ir-block.0):
@@ -48,6 +63,20 @@ define double @fmul_seq(double %start, <4 x double> %vec) {
   ret double %res
 }
 
+define double @fmul_seq_scalar(double %start, <1 x double> %vec) {
+  ; CHECK-LABEL: name: fmul_seq_scalar
+  ; CHECK: bb.1 (%ir-block.0):
+  ; CHECK-NEXT:   liveins: $d0, $d1
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[COPY:%[0-9]+]]:_(s64) = COPY $d0
+  ; CHECK-NEXT:   [[COPY1:%[0-9]+]]:_(s64) = COPY $d1
+  ; CHECK-NEXT:   [[FMUL:%[0-9]+]]:_(s64) = G_FMUL [[COPY]], [[COPY1]]
+  ; CHECK-NEXT:   $d0 = COPY [[FMUL]](s64)
+  ; CHECK-NEXT:   RET_ReallyLR implicit $d0
+  %res = call double @llvm.vector.reduce.fmul.v1f64(double %start, <1 x double> %vec)
+  ret double %res
+}
+
 define double @fmul_fast(double %start, <4 x double> %vec) {
   ; CHECK-LABEL: name: fmul_fast
   ; CHECK: bb.1 (%ir-block.0):