Index: llvm/trunk/lib/Target/RISCV/RISCVISelLowering.h
===================================================================
--- llvm/trunk/lib/Target/RISCV/RISCVISelLowering.h
+++ llvm/trunk/lib/Target/RISCV/RISCVISelLowering.h
@@ -72,6 +72,8 @@
   bool isZExtFree(SDValue Val, EVT VT2) const override;
   bool isSExtCheaperThanZExt(EVT SrcVT, EVT DstVT) const override;
 
+  bool hasBitPreservingFPLogic(EVT VT) const override;
+
   // Provide custom lowering hooks for some operations.
   SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
   void ReplaceNodeResults(SDNode *N, SmallVectorImpl<SDValue> &Results,
Index: llvm/trunk/lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- llvm/trunk/lib/Target/RISCV/RISCVISelLowering.cpp
+++ llvm/trunk/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -302,6 +302,11 @@
   return Subtarget.is64Bit() && SrcVT == MVT::i32 && DstVT == MVT::i64;
 }
 
+bool RISCVTargetLowering::hasBitPreservingFPLogic(EVT VT) const {
+  return (VT == MVT::f32 && Subtarget.hasStdExtF()) ||
+         (VT == MVT::f64 && Subtarget.hasStdExtD());
+}
+
 // Changes the condition code and swaps operands if necessary, so the SetCC
 // operation matches one of the comparisons supported directly in the RISC-V
 // ISA.
Index: llvm/trunk/test/CodeGen/RISCV/float-bit-preserving-dagcombines.ll
===================================================================
--- llvm/trunk/test/CodeGen/RISCV/float-bit-preserving-dagcombines.ll
+++ llvm/trunk/test/CodeGen/RISCV/float-bit-preserving-dagcombines.ll
@@ -0,0 +1,390 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -mattr=+f -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV32F %s
+; RUN: llc -mtriple=riscv32 -mattr=+f,+d -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV32FD %s
+; RUN: llc -mtriple=riscv64 -mattr=+f -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV64F %s
+; RUN: llc -mtriple=riscv64 -mattr=+f,+d -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV64FD %s
+
+; These functions perform extra work to ensure that `%a3` starts in a
+; floating-point register, if the machine has them, and the result of
+; the bitwise operation is then needed in a floating-point register.
+; This should mean the optimisations will fire even if you're using the
+; soft-float ABI on a machine with hardware floating-point support.
+
+define float @bitcast_and(float %a1, float %a2) nounwind {
+; RV32F-LABEL: bitcast_and:
+; RV32F:       # %bb.0:
+; RV32F-NEXT:    fmv.w.x ft0, a1
+; RV32F-NEXT:    fmv.w.x ft1, a0
+; RV32F-NEXT:    fadd.s ft0, ft1, ft0
+; RV32F-NEXT:    fabs.s ft0, ft0
+; RV32F-NEXT:    fadd.s ft0, ft1, ft0
+; RV32F-NEXT:    fmv.x.w a0, ft0
+; RV32F-NEXT:    ret
+;
+; RV32FD-LABEL: bitcast_and:
+; RV32FD:       # %bb.0:
+; RV32FD-NEXT:    fmv.w.x ft0, a1
+; RV32FD-NEXT:    fmv.w.x ft1, a0
+; RV32FD-NEXT:    fadd.s ft0, ft1, ft0
+; RV32FD-NEXT:    fabs.s ft0, ft0
+; RV32FD-NEXT:    fadd.s ft0, ft1, ft0
+; RV32FD-NEXT:    fmv.x.w a0, ft0
+; RV32FD-NEXT:    ret
+;
+; RV64F-LABEL: bitcast_and:
+; RV64F:       # %bb.0:
+; RV64F-NEXT:    fmv.w.x ft0, a1
+; RV64F-NEXT:    fmv.w.x ft1, a0
+; RV64F-NEXT:    fadd.s ft0, ft1, ft0
+; RV64F-NEXT:    fabs.s ft0, ft0
+; RV64F-NEXT:    fadd.s ft0, ft1, ft0
+; RV64F-NEXT:    fmv.x.w a0, ft0
+; RV64F-NEXT:    ret
+;
+; RV64FD-LABEL: bitcast_and:
+; RV64FD:       # %bb.0:
+; RV64FD-NEXT:    fmv.w.x ft0, a1
+; RV64FD-NEXT:    fmv.w.x ft1, a0
+; RV64FD-NEXT:    fadd.s ft0, ft1, ft0
+; RV64FD-NEXT:    fabs.s ft0, ft0
+; RV64FD-NEXT:    fadd.s ft0, ft1, ft0
+; RV64FD-NEXT:    fmv.x.w a0, ft0
+; RV64FD-NEXT:    ret
+  %a3 = fadd float %a1, %a2
+  %bc1 = bitcast float %a3 to i32
+  %and = and i32 %bc1, 2147483647
+  %bc2 = bitcast i32 %and to float
+  %a4 = fadd float %a1, %bc2
+  ret float %a4
+}
+
+define double @bitcast_double_and(double %a1, double %a2) nounwind {
+; RV32F-LABEL: bitcast_double_and:
+; RV32F:       # %bb.0:
+; RV32F-NEXT:    addi sp, sp, -16
+; RV32F-NEXT:    sw ra, 12(sp)
+; RV32F-NEXT:    sw s0, 8(sp)
+; RV32F-NEXT:    sw s1, 4(sp)
+; RV32F-NEXT:    mv s0, a1
+; RV32F-NEXT:    mv s1, a0
+; RV32F-NEXT:    call __adddf3
+; RV32F-NEXT:    mv a2, a0
+; RV32F-NEXT:    lui a0, 524288
+; RV32F-NEXT:    addi a0, a0, -1
+; RV32F-NEXT:    and a3, a1, a0
+; RV32F-NEXT:    mv a0, s1
+; RV32F-NEXT:    mv a1, s0
+; RV32F-NEXT:    call __adddf3
+; RV32F-NEXT:    lw s1, 4(sp)
+; RV32F-NEXT:    lw s0, 8(sp)
+; RV32F-NEXT:    lw ra, 12(sp)
+; RV32F-NEXT:    addi sp, sp, 16
+; RV32F-NEXT:    ret
+;
+; RV32FD-LABEL: bitcast_double_and:
+; RV32FD:       # %bb.0:
+; RV32FD-NEXT:    addi sp, sp, -16
+; RV32FD-NEXT:    sw a2, 8(sp)
+; RV32FD-NEXT:    sw a3, 12(sp)
+; RV32FD-NEXT:    fld ft0, 8(sp)
+; RV32FD-NEXT:    sw a0, 8(sp)
+; RV32FD-NEXT:    sw a1, 12(sp)
+; RV32FD-NEXT:    fld ft1, 8(sp)
+; RV32FD-NEXT:    fadd.d ft0, ft1, ft0
+; RV32FD-NEXT:    fabs.d ft0, ft0
+; RV32FD-NEXT:    fadd.d ft0, ft1, ft0
+; RV32FD-NEXT:    fsd ft0, 8(sp)
+; RV32FD-NEXT:    lw a0, 8(sp)
+; RV32FD-NEXT:    lw a1, 12(sp)
+; RV32FD-NEXT:    addi sp, sp, 16
+; RV32FD-NEXT:    ret
+;
+; RV64F-LABEL: bitcast_double_and:
+; RV64F:       # %bb.0:
+; RV64F-NEXT:    addi sp, sp, -16
+; RV64F-NEXT:    sd ra, 8(sp)
+; RV64F-NEXT:    sd s0, 0(sp)
+; RV64F-NEXT:    mv s0, a0
+; RV64F-NEXT:    call __adddf3
+; RV64F-NEXT:    addi a1, zero, -1
+; RV64F-NEXT:    slli a1, a1, 63
+; RV64F-NEXT:    addi a1, a1, -1
+; RV64F-NEXT:    and a1, a0, a1
+; RV64F-NEXT:    mv a0, s0
+; RV64F-NEXT:    call __adddf3
+; RV64F-NEXT:    ld s0, 0(sp)
+; RV64F-NEXT:    ld ra, 8(sp)
+; RV64F-NEXT:    addi sp, sp, 16
+; RV64F-NEXT:    ret
+;
+; RV64FD-LABEL: bitcast_double_and:
+; RV64FD:       # %bb.0:
+; RV64FD-NEXT:    fmv.d.x ft0, a1
+; RV64FD-NEXT:    fmv.d.x ft1, a0
+; RV64FD-NEXT:    fadd.d ft0, ft1, ft0
+; RV64FD-NEXT:    fabs.d ft0, ft0
+; RV64FD-NEXT:    fadd.d ft0, ft1, ft0
+; RV64FD-NEXT:    fmv.x.d a0, ft0
+; RV64FD-NEXT:    ret
+  %a3 = fadd double %a1, %a2
+  %bc1 = bitcast double %a3 to i64
+  %and = and i64 %bc1, 9223372036854775807
+  %bc2 = bitcast i64 %and to double
+  %a4 = fadd double %a1, %bc2
+  ret double %a4
+}
+
+
+define float @bitcast_xor(float %a1, float %a2) nounwind {
+; RV32F-LABEL: bitcast_xor:
+; RV32F:       # %bb.0:
+; RV32F-NEXT:    fmv.w.x ft0, a1
+; RV32F-NEXT:    fmv.w.x ft1, a0
+; RV32F-NEXT:    fmul.s ft0, ft1, ft0
+; RV32F-NEXT:    fneg.s ft0, ft0
+; RV32F-NEXT:    fmul.s ft0, ft1, ft0
+; RV32F-NEXT:    fmv.x.w a0, ft0
+; RV32F-NEXT:    ret
+;
+; RV32FD-LABEL: bitcast_xor:
+; RV32FD:       # %bb.0:
+; RV32FD-NEXT:    fmv.w.x ft0, a1
+; RV32FD-NEXT:    fmv.w.x ft1, a0
+; RV32FD-NEXT:    fmul.s ft0, ft1, ft0
+; RV32FD-NEXT:    fneg.s ft0, ft0
+; RV32FD-NEXT:    fmul.s ft0, ft1, ft0
+; RV32FD-NEXT:    fmv.x.w a0, ft0
+; RV32FD-NEXT:    ret
+;
+; RV64F-LABEL: bitcast_xor:
+; RV64F:       # %bb.0:
+; RV64F-NEXT:    fmv.w.x ft0, a1
+; RV64F-NEXT:    fmv.w.x ft1, a0
+; RV64F-NEXT:    fmul.s ft0, ft1, ft0
+; RV64F-NEXT:    fneg.s ft0, ft0
+; RV64F-NEXT:    fmul.s ft0, ft1, ft0
+; RV64F-NEXT:    fmv.x.w a0, ft0
+; RV64F-NEXT:    ret
+;
+; RV64FD-LABEL: bitcast_xor:
+; RV64FD:       # %bb.0:
+; RV64FD-NEXT:    fmv.w.x ft0, a1
+; RV64FD-NEXT:    fmv.w.x ft1, a0
+; RV64FD-NEXT:    fmul.s ft0, ft1, ft0
+; RV64FD-NEXT:    fneg.s ft0, ft0
+; RV64FD-NEXT:    fmul.s ft0, ft1, ft0
+; RV64FD-NEXT:    fmv.x.w a0, ft0
+; RV64FD-NEXT:    ret
+  %a3 = fmul float %a1, %a2
+  %bc1 = bitcast float %a3 to i32
+  %and = xor i32 %bc1, 2147483648
+  %bc2 = bitcast i32 %and to float
+  %a4 = fmul float %a1, %bc2
+  ret float %a4
+}
+
+define double @bitcast_double_xor(double %a1, double %a2) nounwind {
+; RV32F-LABEL: bitcast_double_xor:
+; RV32F:       # %bb.0:
+; RV32F-NEXT:    addi sp, sp, -16
+; RV32F-NEXT:    sw ra, 12(sp)
+; RV32F-NEXT:    sw s0, 8(sp)
+; RV32F-NEXT:    sw s1, 4(sp)
+; RV32F-NEXT:    mv s0, a1
+; RV32F-NEXT:    mv s1, a0
+; RV32F-NEXT:    call __muldf3
+; RV32F-NEXT:    mv a2, a0
+; RV32F-NEXT:    lui a0, 524288
+; RV32F-NEXT:    xor a3, a1, a0
+; RV32F-NEXT:    mv a0, s1
+; RV32F-NEXT:    mv a1, s0
+; RV32F-NEXT:    call __muldf3
+; RV32F-NEXT:    lw s1, 4(sp)
+; RV32F-NEXT:    lw s0, 8(sp)
+; RV32F-NEXT:    lw ra, 12(sp)
+; RV32F-NEXT:    addi sp, sp, 16
+; RV32F-NEXT:    ret
+;
+; RV32FD-LABEL: bitcast_double_xor:
+; RV32FD:       # %bb.0:
+; RV32FD-NEXT:    addi sp, sp, -16
+; RV32FD-NEXT:    sw a2, 8(sp)
+; RV32FD-NEXT:    sw a3, 12(sp)
+; RV32FD-NEXT:    fld ft0, 8(sp)
+; RV32FD-NEXT:    sw a0, 8(sp)
+; RV32FD-NEXT:    sw a1, 12(sp)
+; RV32FD-NEXT:    fld ft1, 8(sp)
+; RV32FD-NEXT:    fmul.d ft0, ft1, ft0
+; RV32FD-NEXT:    fneg.d ft0, ft0
+; RV32FD-NEXT:    fmul.d ft0, ft1, ft0
+; RV32FD-NEXT:    fsd ft0, 8(sp)
+; RV32FD-NEXT:    lw a0, 8(sp)
+; RV32FD-NEXT:    lw a1, 12(sp)
+; RV32FD-NEXT:    addi sp, sp, 16
+; RV32FD-NEXT:    ret
+;
+; RV64F-LABEL: bitcast_double_xor:
+; RV64F:       # %bb.0:
+; RV64F-NEXT:    addi sp, sp, -16
+; RV64F-NEXT:    sd ra, 8(sp)
+; RV64F-NEXT:    sd s0, 0(sp)
+; RV64F-NEXT:    mv s0, a0
+; RV64F-NEXT:    call __muldf3
+; RV64F-NEXT:    addi a1, zero, -1
+; RV64F-NEXT:    slli a1, a1, 63
+; RV64F-NEXT:    xor a1, a0, a1
+; RV64F-NEXT:    mv a0, s0
+; RV64F-NEXT:    call __muldf3
+; RV64F-NEXT:    ld s0, 0(sp)
+; RV64F-NEXT:    ld ra, 8(sp)
+; RV64F-NEXT:    addi sp, sp, 16
+; RV64F-NEXT:    ret
+;
+; RV64FD-LABEL: bitcast_double_xor:
+; RV64FD:       # %bb.0:
+; RV64FD-NEXT:    fmv.d.x ft0, a1
+; RV64FD-NEXT:    fmv.d.x ft1, a0
+; RV64FD-NEXT:    fmul.d ft0, ft1, ft0
+; RV64FD-NEXT:    fneg.d ft0, ft0
+; RV64FD-NEXT:    fmul.d ft0, ft1, ft0
+; RV64FD-NEXT:    fmv.x.d a0, ft0
+; RV64FD-NEXT:    ret
+  %a3 = fmul double %a1, %a2
+  %bc1 = bitcast double %a3 to i64
+  %and = xor i64 %bc1, 9223372036854775808
+  %bc2 = bitcast i64 %and to double
+  %a4 = fmul double %a1, %bc2
+  ret double %a4
+}
+
+define float @bitcast_or(float %a1, float %a2) nounwind {
+; RV32F-LABEL: bitcast_or:
+; RV32F:       # %bb.0:
+; RV32F-NEXT:    fmv.w.x ft0, a1
+; RV32F-NEXT:    fmv.w.x ft1, a0
+; RV32F-NEXT:    fmul.s ft0, ft1, ft0
+; RV32F-NEXT:    fabs.s ft0, ft0
+; RV32F-NEXT:    fneg.s ft0, ft0
+; RV32F-NEXT:    fmul.s ft0, ft1, ft0
+; RV32F-NEXT:    fmv.x.w a0, ft0
+; RV32F-NEXT:    ret
+;
+; RV32FD-LABEL: bitcast_or:
+; RV32FD:       # %bb.0:
+; RV32FD-NEXT:    fmv.w.x ft0, a1
+; RV32FD-NEXT:    fmv.w.x ft1, a0
+; RV32FD-NEXT:    fmul.s ft0, ft1, ft0
+; RV32FD-NEXT:    fabs.s ft0, ft0
+; RV32FD-NEXT:    fneg.s ft0, ft0
+; RV32FD-NEXT:    fmul.s ft0, ft1, ft0
+; RV32FD-NEXT:    fmv.x.w a0, ft0
+; RV32FD-NEXT:    ret
+;
+; RV64F-LABEL: bitcast_or:
+; RV64F:       # %bb.0:
+; RV64F-NEXT:    fmv.w.x ft0, a1
+; RV64F-NEXT:    fmv.w.x ft1, a0
+; RV64F-NEXT:    fmul.s ft0, ft1, ft0
+; RV64F-NEXT:    fabs.s ft0, ft0
+; RV64F-NEXT:    fneg.s ft0, ft0
+; RV64F-NEXT:    fmul.s ft0, ft1, ft0
+; RV64F-NEXT:    fmv.x.w a0, ft0
+; RV64F-NEXT:    ret
+;
+; RV64FD-LABEL: bitcast_or:
+; RV64FD:       # %bb.0:
+; RV64FD-NEXT:    fmv.w.x ft0, a1
+; RV64FD-NEXT:    fmv.w.x ft1, a0
+; RV64FD-NEXT:    fmul.s ft0, ft1, ft0
+; RV64FD-NEXT:    fabs.s ft0, ft0
+; RV64FD-NEXT:    fneg.s ft0, ft0
+; RV64FD-NEXT:    fmul.s ft0, ft1, ft0
+; RV64FD-NEXT:    fmv.x.w a0, ft0
+; RV64FD-NEXT:    ret
+  %a3 = fmul float %a1, %a2
+  %bc1 = bitcast float %a3 to i32
+  %and = or i32 %bc1, 2147483648
+  %bc2 = bitcast i32 %and to float
+  %a4 = fmul float %a1, %bc2
+  ret float %a4
+}
+
+define double @bitcast_double_or(double %a1, double %a2) nounwind {
+; RV32F-LABEL: bitcast_double_or:
+; RV32F:       # %bb.0:
+; RV32F-NEXT:    addi sp, sp, -16
+; RV32F-NEXT:    sw ra, 12(sp)
+; RV32F-NEXT:    sw s0, 8(sp)
+; RV32F-NEXT:    sw s1, 4(sp)
+; RV32F-NEXT:    mv s0, a1
+; RV32F-NEXT:    mv s1, a0
+; RV32F-NEXT:    call __muldf3
+; RV32F-NEXT:    mv a2, a0
+; RV32F-NEXT:    lui a0, 524288
+; RV32F-NEXT:    or a3, a1, a0
+; RV32F-NEXT:    mv a0, s1
+; RV32F-NEXT:    mv a1, s0
+; RV32F-NEXT:    call __muldf3
+; RV32F-NEXT:    lw s1, 4(sp)
+; RV32F-NEXT:    lw s0, 8(sp)
+; RV32F-NEXT:    lw ra, 12(sp)
+; RV32F-NEXT:    addi sp, sp, 16
+; RV32F-NEXT:    ret
+;
+; RV32FD-LABEL: bitcast_double_or:
+; RV32FD:       # %bb.0:
+; RV32FD-NEXT:    addi sp, sp, -16
+; RV32FD-NEXT:    sw a2, 8(sp)
+; RV32FD-NEXT:    sw a3, 12(sp)
+; RV32FD-NEXT:    fld ft0, 8(sp)
+; RV32FD-NEXT:    sw a0, 8(sp)
+; RV32FD-NEXT:    sw a1, 12(sp)
+; RV32FD-NEXT:    fld ft1, 8(sp)
+; RV32FD-NEXT:    fmul.d ft0, ft1, ft0
+; RV32FD-NEXT:    fabs.d ft0, ft0
+; RV32FD-NEXT:    fneg.d ft0, ft0
+; RV32FD-NEXT:    fmul.d ft0, ft1, ft0
+; RV32FD-NEXT:    fsd ft0, 8(sp)
+; RV32FD-NEXT:    lw a0, 8(sp)
+; RV32FD-NEXT:    lw a1, 12(sp)
+; RV32FD-NEXT:    addi sp, sp, 16
+; RV32FD-NEXT:    ret
+;
+; RV64F-LABEL: bitcast_double_or:
+; RV64F:       # %bb.0:
+; RV64F-NEXT:    addi sp, sp, -16
+; RV64F-NEXT:    sd ra, 8(sp)
+; RV64F-NEXT:    sd s0, 0(sp)
+; RV64F-NEXT:    mv s0, a0
+; RV64F-NEXT:    call __muldf3
+; RV64F-NEXT:    addi a1, zero, -1
+; RV64F-NEXT:    slli a1, a1, 63
+; RV64F-NEXT:    or a1, a0, a1
+; RV64F-NEXT:    mv a0, s0
+; RV64F-NEXT:    call __muldf3
+; RV64F-NEXT:    ld s0, 0(sp)
+; RV64F-NEXT:    ld ra, 8(sp)
+; RV64F-NEXT:    addi sp, sp, 16
+; RV64F-NEXT:    ret
+;
+; RV64FD-LABEL: bitcast_double_or:
+; RV64FD:       # %bb.0:
+; RV64FD-NEXT:    fmv.d.x ft0, a1
+; RV64FD-NEXT:    fmv.d.x ft1, a0
+; RV64FD-NEXT:    fmul.d ft0, ft1, ft0
+; RV64FD-NEXT:    fabs.d ft0, ft0
+; RV64FD-NEXT:    fneg.d ft0, ft0
+; RV64FD-NEXT:    fmul.d ft0, ft1, ft0
+; RV64FD-NEXT:    fmv.x.d a0, ft0
+; RV64FD-NEXT:    ret
+  %a3 = fmul double %a1, %a2
+  %bc1 = bitcast double %a3 to i64
+  %and = or i64 %bc1, 9223372036854775808
+  %bc2 = bitcast i64 %and to double
+  %a4 = fmul double %a1, %bc2
+  ret double %a4
+}