[LegalizeTypes][RISCV][LoongArch] Optimize promotion of ucmp. (#101366)

ucmp can be promoted with either sext or zext. RISC-V and LoongArch
prefer sext for promoting i32 to i64 unless the inputs are known to be
zero extended already.

This patch uses the existing SExtOrZExtPromotedOperands function that is
used by SETCC promotion to intelligently handle this.

Author: topperc

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

@@ -2294,12 +2294,15 @@ SDValue DAGTypeLegalizer::PromoteIntOp_Shift(SDNode *N) {
 }
 
 SDValue DAGTypeLegalizer::PromoteIntOp_CMP(SDNode *N) {
-  SDValue LHS = N->getOpcode() == ISD::UCMP
-                    ? ZExtPromotedInteger(N->getOperand(0))
-                    : SExtPromotedInteger(N->getOperand(0));
-  SDValue RHS = N->getOpcode() == ISD::UCMP
-                    ? ZExtPromotedInteger(N->getOperand(1))
-                    : SExtPromotedInteger(N->getOperand(1));
+  SDValue LHS = N->getOperand(0);
+  SDValue RHS = N->getOperand(1);
+
+  if (N->getOpcode() == ISD::SCMP) {
+    LHS = SExtPromotedInteger(LHS);
+    RHS = SExtPromotedInteger(RHS);
+  } else {
+    SExtOrZExtPromotedOperands(LHS, RHS);
+  }
 
   return SDValue(DAG.UpdateNodeOperands(N, LHS, RHS), 0);
 }

llvm/test/CodeGen/LoongArch/ucmp.ll

@@ -26,8 +26,8 @@ define i8 @ucmp.8.16(i16 zeroext %x, i16 zeroext %y) nounwind {
 define i8 @ucmp.8.32(i32 %x, i32 %y) nounwind {
 ; CHECK-LABEL: ucmp.8.32:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    bstrpick.d $a1, $a1, 31, 0
-; CHECK-NEXT:    bstrpick.d $a0, $a0, 31, 0
+; CHECK-NEXT:    addi.w $a1, $a1, 0
+; CHECK-NEXT:    addi.w $a0, $a0, 0
 ; CHECK-NEXT:    sltu $a2, $a0, $a1
 ; CHECK-NEXT:    sltu $a0, $a1, $a0
 ; CHECK-NEXT:    sub.d $a0, $a0, $a2
@@ -71,8 +71,8 @@ define i8 @ucmp.8.128(i128 %x, i128 %y) nounwind {
 define i32 @ucmp.32.32(i32 %x, i32 %y) nounwind {
 ; CHECK-LABEL: ucmp.32.32:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    bstrpick.d $a1, $a1, 31, 0
-; CHECK-NEXT:    bstrpick.d $a0, $a0, 31, 0
+; CHECK-NEXT:    addi.w $a1, $a1, 0
+; CHECK-NEXT:    addi.w $a0, $a0, 0
 ; CHECK-NEXT:    sltu $a2, $a0, $a1
 ; CHECK-NEXT:    sltu $a0, $a1, $a0
 ; CHECK-NEXT:    sub.d $a0, $a0, $a2

llvm/test/CodeGen/RISCV/ucmp.ll

@@ -48,10 +48,8 @@ define i8 @ucmp.8.32(i32 %x, i32 %y) nounwind {
 ;
 ; RV64I-LABEL: ucmp.8.32:
 ; RV64I:       # %bb.0:
-; RV64I-NEXT:    slli a1, a1, 32
-; RV64I-NEXT:    srli a1, a1, 32
-; RV64I-NEXT:    slli a0, a0, 32
-; RV64I-NEXT:    srli a0, a0, 32
+; RV64I-NEXT:    sext.w a1, a1
+; RV64I-NEXT:    sext.w a0, a0
 ; RV64I-NEXT:    sltu a2, a0, a1
 ; RV64I-NEXT:    sltu a0, a1, a0
 ; RV64I-NEXT:    sub a0, a0, a2
@@ -164,10 +162,44 @@ define i32 @ucmp.32.32(i32 %x, i32 %y) nounwind {
 ;
 ; RV64I-LABEL: ucmp.32.32:
 ; RV64I:       # %bb.0:
-; RV64I-NEXT:    slli a1, a1, 32
-; RV64I-NEXT:    srli a1, a1, 32
-; RV64I-NEXT:    slli a0, a0, 32
-; RV64I-NEXT:    srli a0, a0, 32
+; RV64I-NEXT:    sext.w a1, a1
+; RV64I-NEXT:    sext.w a0, a0
+; RV64I-NEXT:    sltu a2, a0, a1
+; RV64I-NEXT:    sltu a0, a1, a0
+; RV64I-NEXT:    sub a0, a0, a2
+; RV64I-NEXT:    ret
+  %1 = call i32 @llvm.ucmp(i32 %x, i32 %y)
+  ret i32 %1
+}
+
+define i32 @ucmp.32.32_sext(i32 signext %x, i32 signext %y) nounwind {
+; RV32I-LABEL: ucmp.32.32_sext:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    sltu a2, a0, a1
+; RV32I-NEXT:    sltu a0, a1, a0
+; RV32I-NEXT:    sub a0, a0, a2
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: ucmp.32.32_sext:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    sltu a2, a0, a1
+; RV64I-NEXT:    sltu a0, a1, a0
+; RV64I-NEXT:    sub a0, a0, a2
+; RV64I-NEXT:    ret
+  %1 = call i32 @llvm.ucmp(i32 %x, i32 %y)
+  ret i32 %1
+}
+
+define i32 @ucmp.32.32_zext(i32 zeroext %x, i32 zeroext %y) nounwind {
+; RV32I-LABEL: ucmp.32.32_zext:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    sltu a2, a0, a1
+; RV32I-NEXT:    sltu a0, a1, a0
+; RV32I-NEXT:    sub a0, a0, a2
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: ucmp.32.32_zext:
+; RV64I:       # %bb.0:
 ; RV64I-NEXT:    sltu a2, a0, a1
 ; RV64I-NEXT:    sltu a0, a1, a0
 ; RV64I-NEXT:    sub a0, a0, a2
@@ -179,13 +211,13 @@ define i32 @ucmp.32.32(i32 %x, i32 %y) nounwind {
 define i32 @ucmp.32.64(i64 %x, i64 %y) nounwind {
 ; RV32I-LABEL: ucmp.32.64:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    beq a1, a3, .LBB6_2
+; RV32I-NEXT:    beq a1, a3, .LBB8_2
 ; RV32I-NEXT:  # %bb.1:
 ; RV32I-NEXT:    sltu a4, a1, a3
 ; RV32I-NEXT:    sltu a0, a3, a1
 ; RV32I-NEXT:    sub a0, a0, a4
 ; RV32I-NEXT:    ret
-; RV32I-NEXT:  .LBB6_2:
+; RV32I-NEXT:  .LBB8_2:
 ; RV32I-NEXT:    sltu a4, a0, a2
 ; RV32I-NEXT:    sltu a0, a2, a0
 ; RV32I-NEXT:    sub a0, a0, a4
@@ -204,15 +236,15 @@ define i32 @ucmp.32.64(i64 %x, i64 %y) nounwind {
 define i64 @ucmp.64.64(i64 %x, i64 %y) nounwind {
 ; RV32I-LABEL: ucmp.64.64:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    beq a1, a3, .LBB7_2
+; RV32I-NEXT:    beq a1, a3, .LBB9_2
 ; RV32I-NEXT:  # %bb.1:
 ; RV32I-NEXT:    sltu a4, a1, a3
 ; RV32I-NEXT:    sltu a0, a3, a1
-; RV32I-NEXT:    j .LBB7_3
-; RV32I-NEXT:  .LBB7_2:
+; RV32I-NEXT:    j .LBB9_3
+; RV32I-NEXT:  .LBB9_2:
 ; RV32I-NEXT:    sltu a4, a0, a2
 ; RV32I-NEXT:    sltu a0, a2, a0
-; RV32I-NEXT:  .LBB7_3:
+; RV32I-NEXT:  .LBB9_3:
 ; RV32I-NEXT:    sub a0, a0, a4
 ; RV32I-NEXT:    srai a1, a0, 31
 ; RV32I-NEXT:    ret