[RISCV]Enable isIntDivCheap when attribute is minsize

Don't expand divisions by constants when attribute is minsize.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D130543

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -7010,8 +7010,9 @@ void RISCVTargetLowering::ReplaceNodeResults(SDNode *N,
            "Unexpected custom legalisation");
     // Don't promote division/remainder by constant since we should expand those
     // to multiply by magic constant.
-    // FIXME: What if the expansion is disabled for minsize.
-    if (N->getOperand(1).getOpcode() == ISD::Constant)
+    AttributeList Attr = DAG.getMachineFunction().getFunction().getAttributes();
+    if (N->getOperand(1).getOpcode() == ISD::Constant &&
+        !isIntDivCheap(N->getValueType(0), Attr))
       return;
 
     // If the input is i32, use ANY_EXTEND since the W instructions don't read
@@ -12533,6 +12534,14 @@ RISCVTargetLowering::BuildSDIVPow2(SDNode *N, const APInt &Divisor,
   return DAG.getNode(ISD::SUB, DL, VT, DAG.getConstant(0, DL, VT), SRA);
 }
 
+bool RISCVTargetLowering::isIntDivCheap(EVT VT, AttributeList Attr) const {
+  // When aggressively optimizing for code size, we prefer to use a div
+  // instruction, as it is usually smaller than the alternative sequence.
+  // TODO: Add vector division?
+  bool OptSize = Attr.hasFnAttr(Attribute::MinSize);
+  return OptSize && !VT.isVector();
+}
+
 #define GET_REGISTER_MATCHER
 #include "RISCVGenAsmMatcher.inc"
 

llvm/lib/Target/RISCV/RISCVISelLowering.h

@@ -381,6 +381,8 @@ class RISCVTargetLowering : public TargetLowering {
   bool isFPImmLegal(const APFloat &Imm, EVT VT,
                     bool ForCodeSize) const override;
 
+  bool isIntDivCheap(EVT VT, AttributeList Attr) const override;
+
   bool softPromoteHalfType() const override { return true; }
 
   /// Return the register type for a given MVT, ensuring vectors are treated

llvm/test/CodeGen/RISCV/div_minsize.ll

@@ -0,0 +1,71 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -mattr=+m -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefixes=RV32IM %s
+; RUN: llc -mtriple=riscv64 -mattr=+m -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefixes=RV64IM %s
+
+define i32 @testsize1(i32 %x) minsize nounwind {
+; RV32IM-LABEL: testsize1:
+; RV32IM:       # %bb.0: # %entry
+; RV32IM-NEXT:    li a1, 32
+; RV32IM-NEXT:    div a0, a0, a1
+; RV32IM-NEXT:    ret
+;
+; RV64IM-LABEL: testsize1:
+; RV64IM:       # %bb.0: # %entry
+; RV64IM-NEXT:    li a1, 32
+; RV64IM-NEXT:    divw a0, a0, a1
+; RV64IM-NEXT:    ret
+entry:
+  %div = sdiv i32 %x, 32
+  ret i32 %div
+}
+
+define i32 @testsize2(i32 %x) minsize nounwind {
+; RV32IM-LABEL: testsize2:
+; RV32IM:       # %bb.0: # %entry
+; RV32IM-NEXT:    li a1, 33
+; RV32IM-NEXT:    div a0, a0, a1
+; RV32IM-NEXT:    ret
+;
+; RV64IM-LABEL: testsize2:
+; RV64IM:       # %bb.0: # %entry
+; RV64IM-NEXT:    li a1, 33
+; RV64IM-NEXT:    divw a0, a0, a1
+; RV64IM-NEXT:    ret
+entry:
+  %div = sdiv i32 %x, 33
+  ret i32 %div
+}
+
+define i32 @testsize3(i32 %x) minsize nounwind {
+; RV32IM-LABEL: testsize3:
+; RV32IM:       # %bb.0: # %entry
+; RV32IM-NEXT:    srli a0, a0, 5
+; RV32IM-NEXT:    ret
+;
+; RV64IM-LABEL: testsize3:
+; RV64IM:       # %bb.0: # %entry
+; RV64IM-NEXT:    srliw a0, a0, 5
+; RV64IM-NEXT:    ret
+entry:
+  %div = udiv i32 %x, 32
+  ret i32 %div
+}
+
+define i32 @testsize4(i32 %x) minsize nounwind {
+; RV32IM-LABEL: testsize4:
+; RV32IM:       # %bb.0:
+; RV32IM-NEXT:    li a1, 33
+; RV32IM-NEXT:    divu a0, a0, a1
+; RV32IM-NEXT:    ret
+;
+; RV64IM-LABEL: testsize4:
+; RV64IM:       # %bb.0:
+; RV64IM-NEXT:    li a1, 33
+; RV64IM-NEXT:    divuw a0, a0, a1
+; RV64IM-NEXT:    ret
+  %div = udiv i32 %x, 33
+  ret i32 %div
+}
+