[llvm] [DAG] Improved handling of ISD::ROTL and ISD::ROTR in isKnownToBeAPowerOfTwo (PR #182744)

[Simon Pilgrim via llvm-commits]

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@@ -1006,3 +1008,73 @@ define i32 @pow2_blsi_sub(i32 %x, i32 %a) {
   %r = and i32 %x_sub_y, %y
   ret i32 %r
 }
+
+define i1 @pow2_rotl_extract_vec(<4 x i32> %a0, <4 x i32> %rotamt, i32 %x) {
+; CHECK-LABEL: pow2_rotl_extract_vec:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    pxor %xmm2, %xmm2
+; CHECK-NEXT:    pcmpgtd %xmm0, %xmm2
+; CHECK-NEXT:    movl $4096, %eax # imm = 0x1000
+; CHECK-NEXT:    movd %eax, %xmm0
+; CHECK-NEXT:    movl $1024, %eax # imm = 0x400
+; CHECK-NEXT:    movd %eax, %xmm3
+; CHECK-NEXT:    pand %xmm2, %xmm3
+; CHECK-NEXT:    pandn %xmm0, %xmm2
+; CHECK-NEXT:    por %xmm2, %xmm3
+; CHECK-NEXT:    pslld $23, %xmm1
+; CHECK-NEXT:    pand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm1
+; CHECK-NEXT:    paddd {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm1
+; CHECK-NEXT:    cvttps2dq %xmm1, %xmm0
+; CHECK-NEXT:    pmuludq %xmm3, %xmm0
+; CHECK-NEXT:    pshufd {{.*#+}} xmm1 = xmm0[1,1,3,3]
+; CHECK-NEXT:    por %xmm0, %xmm1
+; CHECK-NEXT:    movd %xmm1, %eax
+; CHECK-NEXT:    notl %edi
+; CHECK-NEXT:    testl %edi, %eax
+; CHECK-NEXT:    sete %al
+; CHECK-NEXT:    retq
+
+  %cmp = icmp sgt <4 x i32> zeroinitializer, %a0
+  %powvec = select <4 x i1> %cmp, <4 x i32> <i32 1024, i32 1235, i32 2048, i32 4096>, <4 x i32> <i32 4096, i32 5679, i32 8192, i32 16384>
+  %d = call <4 x i32> @llvm.fshl.v4i32(<4 x i32> %powvec, <4 x i32> %powvec, <4 x i32> %rotamt)
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RKSimon wrote:

add a `store <4 x i32> %d, ptrp %p` to ensure that this doesn't get scalarised - see #183918

https://github.com/llvm/llvm-project/pull/182744