[llvm] [Codegen][LegalizeIntegerTypes] Improve shift through stack (PR #96151)

[via llvm-commits]

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@@ -723,98 +723,117 @@ define void @lshr_16bytes(ptr %src.ptr, ptr %byteOff.ptr, ptr %dst) nounwind {
 ;
 ; RV32I-LABEL: lshr_16bytes:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    addi sp, sp, -48
-; RV32I-NEXT:    sw s0, 44(sp) # 4-byte Folded Spill
-; RV32I-NEXT:    sw s1, 40(sp) # 4-byte Folded Spill
-; RV32I-NEXT:    sw s2, 36(sp) # 4-byte Folded Spill
-; RV32I-NEXT:    lbu a3, 0(a0)
-; RV32I-NEXT:    lbu a4, 1(a0)
+; RV32I-NEXT:    addi sp, sp, -32
+; RV32I-NEXT:    lbu a3, 1(a0)
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futog wrote:

I will add some tests where the shift amount is known to be a multiple of 4 bytes, so 1 load with an offset is enough to do the shift.

https://github.com/llvm/llvm-project/pull/96151