[llvm] [X86] LowerShiftByScalarImmediate - move shl(x,1) -> add(freeze(x),freeze(x)) to X86FixupInstTunings (PR #161007)

[Simon Pilgrim via llvm-commits]

================
@@ -3543,26 +3543,26 @@ define <2 x i64> @test_128_i64_x_2_140737488289792_mask_shl_18(<2 x i64> %a0) {
 define <2 x i64> @test_128_i64_x_2_18446744065119617024_mask_shl_1(<2 x i64> %a0) {
 ; X86-SSE2-LABEL: test_128_i64_x_2_18446744065119617024_mask_shl_1:
 ; X86-SSE2:       # %bb.0:
-; X86-SSE2-NEXT:    pand {{\.?LCPI[0-9]+_[0-9]+}}, %xmm0
 ; X86-SSE2-NEXT:    paddq %xmm0, %xmm0
+; X86-SSE2-NEXT:    pand {{\.?LCPI[0-9]+_[0-9]+}}, %xmm0
 ; X86-SSE2-NEXT:    retl
 ;
 ; X86-AVX-LABEL: test_128_i64_x_2_18446744065119617024_mask_shl_1:
 ; X86-AVX:       # %bb.0:
-; X86-AVX-NEXT:    vpand {{\.?LCPI[0-9]+_[0-9]+}}, %xmm0, %xmm0
 ; X86-AVX-NEXT:    vpaddq %xmm0, %xmm0, %xmm0
+; X86-AVX-NEXT:    vpand {{\.?LCPI[0-9]+_[0-9]+}}, %xmm0, %xmm0
 ; X86-AVX-NEXT:    retl
 ;
 ; X64-SSE2-LABEL: test_128_i64_x_2_18446744065119617024_mask_shl_1:
 ; X64-SSE2:       # %bb.0:
-; X64-SSE2-NEXT:    pand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
 ; X64-SSE2-NEXT:    paddq %xmm0, %xmm0
+; X64-SSE2-NEXT:    pand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
 ; X64-SSE2-NEXT:    retq
 ;
 ; X64-AVX-LABEL: test_128_i64_x_2_18446744065119617024_mask_shl_1:
 ; X64-AVX:       # %bb.0:
-; X64-AVX-NEXT:    vpand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0, %xmm0
 ; X64-AVX-NEXT:    vpaddq %xmm0, %xmm0, %xmm0
+; X64-AVX-NEXT:    vpand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0, %xmm0
----------------
RKSimon wrote:

The constant has changed as you'd expect:
```
.LCPI0_0:
  .quad -8589934592 # 0xfffffffe00000000
  .quad -8589934592 # 0xfffffffe00000000
test_128_i64_x_2_18446744065119617024_mask_shl_1: # @test_128_i64_x_2_18446744065119617024_mask_shl_1
  pand .LCPI0_0(%rip), %xmm0
  paddq %xmm0, %xmm0
  retq
```
->
```
.LCPI0_0:
  .quad   -17179869184                    # 0xfffffffc00000000
  .quad   -17179869184                    # 0xfffffffc00000000
test_128_i64_x_2_18446744065119617024_mask_shl_1: # @test_128_i64_x_2_18446744065119617024_mask_shl_1
  paddq   %xmm0, %xmm0
  pand    .LCPI0_0(%rip), %xmm0
  retq
```

https://github.com/llvm/llvm-project/pull/161007