[PowerPC] Skip combine for vector_shuffles when two scalar_to_vector nodes are different vector types.

[amyk]

Summary

Currently in combineVectorShuffle(), we update the shuffle mask if either
input vector comes from a scalar_to_vector, and we keep the respective input
vectors in its permuted form by producing PPCISD::SCALAR_TO_VECTOR_PERMUTED.

However, it is possible that we end up in a situation where both input vectors
to the vector_shuffle are scalar_to_vector, and are different vector types.
In situations like this, the shuffle mask is updated incorrectly as the current
code assumes both scalar_to_vector inputs are the same vector type.

This patch skips the combines for vector_shuffle if both input vectors are
scalar_to_vector, and if they are of different vector types. A follow up patch
will focus on fixing this issue afterwards, in order to correctly update the
shuffle mask.

[nemanjai]

LGTM. Thanks for the fix.

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

SDValue PPCTargetLowering::combineVectorShuffle(ShuffleVectorSDNode *SVN,
 
   // Adjust the shuffle mask if either input vector comes from a
   // SCALAR_TO_VECTOR and keep the respective input vector in permuted
   // form (to prevent the need for a swap).
   SmallVector<int, 16> ShuffV(Mask.begin(), Mask.end());
   SDValue SToVLHS = isScalarToVec(LHS);
   SDValue SToVRHS = isScalarToVec(RHS);
   if (SToVLHS || SToVRHS) {
+    // FIXME: If both LHS and RHS are SCALAR_TO_VECTOR, but are not the
+    // same type and have differing element sizes, then do not perform
+    // the following transformation. The current transformation for
+    // SCALAR_TO_VECTOR assumes that both input vectors have the same
+    // element size. This will be updated in the future to account for
+    // differing sizes of the LHS and RHS.
+    if (SToVLHS && SToVRHS &&
+        (SToVLHS.getValueType().getScalarSizeInBits() !=
+         SToVRHS.getValueType().getScalarSizeInBits()))
+      return Res;
+
     int NumEltsIn = SToVLHS ? SToVLHS.getValueType().getVectorNumElements()
                             : SToVRHS.getValueType().getVectorNumElements();
     int NumEltsOut = ShuffV.size();
     // The width of the "valid lane" (i.e. the lane that contains the value that
     // is vectorized) needs to be expressed in terms of the number of elements
     // of the shuffle. It is thereby the ratio of the values before and after
     // any bitcast.
     unsigned ValidLaneWidth =

llvm/test/CodeGen/PowerPC/p8-scalar_vector_conversions.ll

 ; CHECK-LE:       # %bb.0: # %entry
 ; CHECK-LE-NEXT:    addis r3, r2, .LC0@toc@ha
 ; CHECK-LE-NEXT:    ld r3, .LC0@toc@l(r3)
 ; CHECK-LE-NEXT:    lxvdsx v2, 0, r3
 ; CHECK-LE-NEXT:    blr
 ;
 ; CHECK-AIX-LABEL: buildd:
 ; CHECK-AIX:       # %bb.0: # %entry
-; CHECK-AIX-NEXT:    ld 3, L..C0(2)
+; CHECK-AIX-NEXT:    ld 3, L..C0(2) # @d
 ; CHECK-AIX-NEXT:    lxvdsx 34, 0, 3
 ; CHECK-AIX-NEXT:    blr
 entry:
   %0 = load double, double* @d, align 8
   %splat.splatinsert = insertelement <2 x double> undef, double %0, i32 0
   %splat.splat = shufflevector <2 x double> %splat.splatinsert, <2 x double> undef, <2 x i32> zeroinitializer
   ret <2 x double> %splat.splat
 

 ; CHECK-NEXT:    sldi r4, r4, 32
 ; CHECK-NEXT:    mtfprd f1, r3
 ; CHECK-NEXT:    mtfprd f0, r4
 ; CHECK-NEXT:    xxmrghd v2, vs0, vs1
 ; CHECK-NEXT:    blr
 ;
 ; CHECK-LE-LABEL: buildi2:
 ; CHECK-LE:       # %bb.0: # %entry
-; CHECK-LE-NEXT:    mtfprwz f0, r4
+; CHECK-LE-NEXT:    mtfprd f0, r4
 ; CHECK-LE-NEXT:    mtfprd f1, r3
-; CHECK-LE-NEXT:    xxmrgld v2, vs1, vs0
+; CHECK-LE-NEXT:    xxswapd vs0, vs0
+; CHECK-LE-NEXT:    xxswapd v2, vs1
+; CHECK-LE-NEXT:    xxmrgld v2, v2, vs0
 ; CHECK-LE-NEXT:    blr
 ;
 ; CHECK-AIX-LABEL: buildi2:
 ; CHECK-AIX:       # %bb.0: # %entry
 ; CHECK-AIX-NEXT:    sldi 4, 4, 32
 ; CHECK-AIX-NEXT:    mtfprd 1, 3
 ; CHECK-AIX-NEXT:    mtfprd 0, 4
 ; CHECK-AIX-NEXT:    xxmrghd 34, 0, 1
 ; CHECK-AIX-NEXT:    blr
 entry:
   %lhs.i32 = insertelement <4 x i32> undef, i32 %arg1, i32 0
   %rhs = insertelement <2 x i64> undef, i64 %arg, i32 0
   %lhs = bitcast <4 x i32> %lhs.i32 to <2 x i64>
   %shuffle = shufflevector <2 x i64> %lhs, <2 x i64> %rhs, <2 x i32> <i32 0, i32 2>
   ret <2 x i64> %shuffle
 }

llvm/test/CodeGen/PowerPC/scalar_to_vector_shuffle.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -verify-machineinstrs -mcpu=pwr8 -ppc-asm-full-reg-names \
+; RUN:   -ppc-vsr-nums-as-vr -mtriple=powerpc64le-unknown-linux-gnu < %s | \
+; RUN: FileCheck %s --check-prefix=CHECK-LE-P8
+; RUN: llc -verify-machineinstrs -mcpu=pwr9 -ppc-asm-full-reg-names \
+; RUN:   -ppc-vsr-nums-as-vr -mtriple=powerpc64le-unknown-linux-gnu < %s | \
+; RUN: FileCheck %s --check-prefix=CHECK-LE-P9
+; RUN: llc -verify-machineinstrs -mcpu=pwr8 -ppc-asm-full-reg-names \
+; RUN:   -ppc-vsr-nums-as-vr -mtriple=powerpc64-unknown-linux-gnu < %s | \
+; RUN: FileCheck %s --check-prefix=CHECK-BE-P8
+; RUN: llc -verify-machineinstrs -mcpu=pwr9 -ppc-asm-full-reg-names \
+; RUN:   -ppc-vsr-nums-as-vr -mtriple=powerpc64-unknown-linux-gnu < %s | \
+; RUN: FileCheck %s --check-prefix=CHECK-BE-P9
+
+; RUN: llc -verify-machineinstrs -mcpu=pwr8 -ppc-asm-full-reg-names \
+; RUN:   -ppc-vsr-nums-as-vr -mtriple=powerpc64-ibm-aix < %s | \
+; RUN: FileCheck %s --check-prefix=CHECK-AIX-64-P8
+; RUN: llc -verify-machineinstrs -mcpu=pwr9 -ppc-asm-full-reg-names \
+; RUN:   -ppc-vsr-nums-as-vr -mtriple=powerpc64-ibm-aix < %s | \
+; RUN: FileCheck %s --check-prefix=CHECK-AIX-64-P9
+; RUN: llc -verify-machineinstrs -mcpu=pwr8 -ppc-asm-full-reg-names \
+; RUN:   -ppc-vsr-nums-as-vr -mtriple=powerpc-ibm-aix < %s | \
+; RUN: FileCheck %s --check-prefix=CHECK-AIX-32-P8
+; RUN: llc -verify-machineinstrs -mcpu=pwr9 -ppc-asm-full-reg-names \
+; RUN:   -ppc-vsr-nums-as-vr -mtriple=powerpc-ibm-aix < %s | \
+; RUN: FileCheck %s --check-prefix=CHECK-AIX-32-P9
+
+define <16 x i8> @test_4_8(ptr nocapture noundef readonly %a, ptr nocapture noundef readonly %b) local_unnamed_addr {
+; CHECK-LE-P8-LABEL: test_4_8:
+; CHECK-LE-P8:       # %bb.0: # %entry
+; CHECK-LE-P8-NEXT:    lfiwzx f0, 0, r3
+; CHECK-LE-P8-NEXT:    lfdx f1, 0, r4
+; CHECK-LE-P8-NEXT:    addis r5, r2, .LCPI0_0@toc@ha
+; CHECK-LE-P8-NEXT:    addi r3, r5, .LCPI0_0@toc@l
+; CHECK-LE-P8-NEXT:    lvx v4, 0, r3
+; CHECK-LE-P8-NEXT:    xxswapd v2, f0
+; CHECK-LE-P8-NEXT:    xxswapd v3, f1
+; CHECK-LE-P8-NEXT:    vperm v2, v3, v2, v4
+; CHECK-LE-P8-NEXT:    blr
+;
+; CHECK-LE-P9-LABEL: test_4_8:
+; CHECK-LE-P9:       # %bb.0: # %entry
+; CHECK-LE-P9-NEXT:    lfiwzx f0, 0, r3
+; CHECK-LE-P9-NEXT:    addis r3, r2, .LCPI0_0@toc@ha
+; CHECK-LE-P9-NEXT:    addi r3, r3, .LCPI0_0@toc@l
+; CHECK-LE-P9-NEXT:    xxswapd v2, f0
+; CHECK-LE-P9-NEXT:    lfd f0, 0(r4)
+; CHECK-LE-P9-NEXT:    lxv v4, 0(r3)
+; CHECK-LE-P9-NEXT:    xxswapd v3, f0
+; CHECK-LE-P9-NEXT:    vperm v2, v3, v2, v4
+; CHECK-LE-P9-NEXT:    blr
+;
+; CHECK-BE-P8-LABEL: test_4_8:
+; CHECK-BE-P8:       # %bb.0: # %entry
+; CHECK-BE-P8-NEXT:    lfiwzx f0, 0, r3
+; CHECK-BE-P8-NEXT:    addis r5, r2, .LCPI0_0@toc@ha
+; CHECK-BE-P8-NEXT:    lxsdx v3, 0, r4
+; CHECK-BE-P8-NEXT:    addi r3, r5, .LCPI0_0@toc@l
+; CHECK-BE-P8-NEXT:    lxvw4x v4, 0, r3
+; CHECK-BE-P8-NEXT:    xxsldwi v2, f0, f0, 1
+; CHECK-BE-P8-NEXT:    vperm v2, v2, v3, v4
+; CHECK-BE-P8-NEXT:    blr
+;
+; CHECK-BE-P9-LABEL: test_4_8:
+; CHECK-BE-P9:       # %bb.0: # %entry
+; CHECK-BE-P9-NEXT:    lfiwzx f0, 0, r3
+; CHECK-BE-P9-NEXT:    addis r3, r2, .LCPI0_0@toc@ha
+; CHECK-BE-P9-NEXT:    lxsd v3, 0(r4)
+; CHECK-BE-P9-NEXT:    addi r3, r3, .LCPI0_0@toc@l
+; CHECK-BE-P9-NEXT:    lxv v4, 0(r3)
+; CHECK-BE-P9-NEXT:    xxsldwi v2, f0, f0, 1
+; CHECK-BE-P9-NEXT:    vperm v2, v2, v3, v4
+; CHECK-BE-P9-NEXT:    blr
+;
+; CHECK-AIX-64-P8-LABEL: test_4_8:
+; CHECK-AIX-64-P8:       # %bb.0: # %entry
+; CHECK-AIX-64-P8-NEXT:    ld r5, L..C0(r2) # %const.0
+; CHECK-AIX-64-P8-NEXT:    lfiwzx f0, 0, r3
+; CHECK-AIX-64-P8-NEXT:    lxsdx v3, 0, r4
+; CHECK-AIX-64-P8-NEXT:    xxsldwi v2, f0, f0, 1
+; CHECK-AIX-64-P8-NEXT:    lxvw4x v4, 0, r5
+; CHECK-AIX-64-P8-NEXT:    vperm v2, v2, v3, v4
+; CHECK-AIX-64-P8-NEXT:    blr
+;
+; CHECK-AIX-64-P9-LABEL: test_4_8:
+; CHECK-AIX-64-P9:       # %bb.0: # %entry
+; CHECK-AIX-64-P9-NEXT:    lfiwzx f0, 0, r3
+; CHECK-AIX-64-P9-NEXT:    ld r3, L..C0(r2) # %const.0
+; CHECK-AIX-64-P9-NEXT:    lxsd v3, 0(r4)
+; CHECK-AIX-64-P9-NEXT:    xxsldwi v2, f0, f0, 1
+; CHECK-AIX-64-P9-NEXT:    lxv v4, 0(r3)
+; CHECK-AIX-64-P9-NEXT:    vperm v2, v2, v3, v4
+; CHECK-AIX-64-P9-NEXT:    blr
+;
+; CHECK-AIX-32-P8-LABEL: test_4_8:
+; CHECK-AIX-32-P8:       # %bb.0: # %entry
+; CHECK-AIX-32-P8-NEXT:    lwz r5, 4(r4)
+; CHECK-AIX-32-P8-NEXT:    lxsiwzx v2, 0, r3
+; CHECK-AIX-32-P8-NEXT:    stw r5, -16(r1)
+; CHECK-AIX-32-P8-NEXT:    lwz r3, 0(r4)
+; CHECK-AIX-32-P8-NEXT:    addi r4, r1, -32
+; CHECK-AIX-32-P8-NEXT:    stw r3, -32(r1)
+; CHECK-AIX-32-P8-NEXT:    addi r3, r1, -16
+; CHECK-AIX-32-P8-NEXT:    lxvw4x vs0, 0, r3
+; CHECK-AIX-32-P8-NEXT:    lwz r3, L..C0(r2) # %const.0
+; CHECK-AIX-32-P8-NEXT:    lxvw4x vs1, 0, r4
+; CHECK-AIX-32-P8-NEXT:    lxvw4x v4, 0, r3
+; CHECK-AIX-32-P8-NEXT:    xxmrghw v3, vs1, vs0
+; CHECK-AIX-32-P8-NEXT:    vperm v2, v2, v3, v4
+; CHECK-AIX-32-P8-NEXT:    blr
+;
+; CHECK-AIX-32-P9-LABEL: test_4_8:
+; CHECK-AIX-32-P9:       # %bb.0: # %entry
+; CHECK-AIX-32-P9-NEXT:    lxsiwzx v2, 0, r3
+; CHECK-AIX-32-P9-NEXT:    lwz r3, 4(r4)
+; CHECK-AIX-32-P9-NEXT:    stw r3, -16(r1)
+; CHECK-AIX-32-P9-NEXT:    lwz r3, 0(r4)
+; CHECK-AIX-32-P9-NEXT:    lxv vs0, -16(r1)
+; CHECK-AIX-32-P9-NEXT:    stw r3, -32(r1)
+; CHECK-AIX-32-P9-NEXT:    lwz r3, L..C0(r2) # %const.0
+; CHECK-AIX-32-P9-NEXT:    lxv vs1, -32(r1)
+; CHECK-AIX-32-P9-NEXT:    lxv v4, 0(r3)
+; CHECK-AIX-32-P9-NEXT:    xxmrghw v3, vs1, vs0
+; CHECK-AIX-32-P9-NEXT:    vperm v2, v2, v3, v4
+; CHECK-AIX-32-P9-NEXT:    blr
+entry:
+  %0 = load <4 x i8>, ptr %a, align 4
+  %bc1 = bitcast <4 x i8> %0 to i32
+  %vecinit3 = insertelement <4 x i32> poison, i32 %bc1, i64 0
+  %1 = load <8 x i8>, ptr %b, align 8
+  %bc2 = bitcast <8 x i8> %1 to i64
+  %vecinit6 = insertelement <2 x i64> undef, i64 %bc2, i64 0
+  %2 = bitcast <4 x i32> %vecinit3 to <16 x i8>
+  %3 = bitcast <2 x i64> %vecinit6 to <16 x i8>
+  %shuffle = shufflevector <16 x i8> %2, <16 x i8> %3, <16 x i32> <i32 0, i32 1, i32 16, i32 17, i32 18, i32 19, i32 20, i32 21, i32 22, i32 23, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
+  ret <16 x i8> %shuffle
+}