[RISCV] Add support for call returns to RISCVSExtWRemoval.

The implementation is inspired by code from PPCInstrInfo.

We look for a copy from X10(A0) preceded by an ADJCALLSTACKUP and
a PseudoCall. We use the PseudoCall to look up the IR function being
called to find it's return attributes.

Reviewed By: asb

Differential Revision: https://reviews.llvm.org/D139808

diff --git a/llvm/lib/Target/RISCV/RISCVSExtWRemoval.cpp b/llvm/lib/Target/RISCV/RISCVSExtWRemoval.cpp
index d505c3c..8065863 100644 (file)
--- a/llvm/lib/Target/RISCV/RISCVSExtWRemoval.cpp
+++ b/llvm/lib/Target/RISCV/RISCVSExtWRemoval.cpp
@@ -365,9 +365,42 @@ static bool isSignExtendedW(Register SrcReg, MachineRegisterInfo &MRI,
           continue;
       }
 
-      // TODO: Handle returns from calls?
+      Register CopySrcReg = MI->getOperand(1).getReg();
+      if (CopySrcReg == RISCV::X10) {
+        // For a method return value, we check the ZExt/SExt flags in attribute.
+        // We assume the following code sequence for method call.
+        // PseudoCALL @bar, ...
+        // ADJCALLSTACKUP 0, 0, implicit-def dead $x2, implicit $x2
+        // %0:gpr = COPY $x10
+        //
+        // We use the PseudoCall to look up the IR function being called to find
+        // its return attributes.
+        const MachineBasicBlock *MBB = MI->getParent();
+        auto II = MI->getIterator();
+        if (II == MBB->instr_begin() ||
+            (--II)->getOpcode() != RISCV::ADJCALLSTACKUP)
+          return false;
 
-      if (!AddRegDefToWorkList(MI->getOperand(1).getReg()))
+        const MachineInstr &CallMI = *(--II);
+        if (!CallMI.isCall() || !CallMI.getOperand(0).isGlobal())
+          return false;
+
+        auto *CalleeFn =
+            dyn_cast_if_present<Function>(CallMI.getOperand(0).getGlobal());
+        if (!CalleeFn)
+          return false;
+
+        auto *IntTy = dyn_cast<IntegerType>(CalleeFn->getReturnType());
+        if (!IntTy)
+          return false;
+
+        const AttributeSet &Attrs = CalleeFn->getAttributes().getRetAttrs();
+        unsigned BitWidth = IntTy->getBitWidth();
+        return (BitWidth <= 32 && Attrs.hasAttribute(Attribute::SExt)) ||
+               (BitWidth < 32 && Attrs.hasAttribute(Attribute::ZExt));
+      }
+
+      if (!AddRegDefToWorkList(CopySrcReg))
         return false;
 
       break;

diff --git a/llvm/test/CodeGen/RISCV/sextw-removal.ll b/llvm/test/CodeGen/RISCV/sextw-removal.ll
index 963fe7c..23ea715 100644 (file)
--- a/llvm/test/CodeGen/RISCV/sextw-removal.ll
+++ b/llvm/test/CodeGen/RISCV/sextw-removal.ll
@@ -1146,3 +1146,123 @@ cleanup:                                          ; preds = %entry, %if.end
   %retval.0 = phi i32 [ %r.4, %if.end ], [ 0, %entry ]
   ret i32 %retval.0
 }
+
+define void @test16(i32 signext %arg, i32 signext %arg1) nounwind {
+; CHECK-LABEL: test16:
+; CHECK:       # %bb.0: # %bb
+; CHECK-NEXT:    addi sp, sp, -32
+; CHECK-NEXT:    sd ra, 24(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    sd s0, 16(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    sd s1, 8(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    mv s0, a1
+; CHECK-NEXT:    call bar@plt
+; CHECK-NEXT:    mv s1, a0
+; CHECK-NEXT:  .LBB19_1: # %bb2
+; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    mv a0, s1
+; CHECK-NEXT:    call bar@plt
+; CHECK-NEXT:    sllw s1, s1, s0
+; CHECK-NEXT:    bnez a0, .LBB19_1
+; CHECK-NEXT:  # %bb.2: # %bb7
+; CHECK-NEXT:    ld ra, 24(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    ld s0, 16(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    ld s1, 8(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    addi sp, sp, 32
+; CHECK-NEXT:    ret
+;
+; NOREMOVAL-LABEL: test16:
+; NOREMOVAL:       # %bb.0: # %bb
+; NOREMOVAL-NEXT:    addi sp, sp, -32
+; NOREMOVAL-NEXT:    sd ra, 24(sp) # 8-byte Folded Spill
+; NOREMOVAL-NEXT:    sd s0, 16(sp) # 8-byte Folded Spill
+; NOREMOVAL-NEXT:    sd s1, 8(sp) # 8-byte Folded Spill
+; NOREMOVAL-NEXT:    mv s0, a1
+; NOREMOVAL-NEXT:    call bar@plt
+; NOREMOVAL-NEXT:    mv s1, a0
+; NOREMOVAL-NEXT:  .LBB19_1: # %bb2
+; NOREMOVAL-NEXT:    # =>This Inner Loop Header: Depth=1
+; NOREMOVAL-NEXT:    sext.w a0, s1
+; NOREMOVAL-NEXT:    call bar@plt
+; NOREMOVAL-NEXT:    sllw s1, s1, s0
+; NOREMOVAL-NEXT:    bnez a0, .LBB19_1
+; NOREMOVAL-NEXT:  # %bb.2: # %bb7
+; NOREMOVAL-NEXT:    ld ra, 24(sp) # 8-byte Folded Reload
+; NOREMOVAL-NEXT:    ld s0, 16(sp) # 8-byte Folded Reload
+; NOREMOVAL-NEXT:    ld s1, 8(sp) # 8-byte Folded Reload
+; NOREMOVAL-NEXT:    addi sp, sp, 32
+; NOREMOVAL-NEXT:    ret
+bb:
+  %i = call signext i32 @bar(i32 signext %arg)
+  br label %bb2
+
+bb2:                                              ; preds = %bb2, %bb
+  %i3 = phi i32 [ %i, %bb ], [ %i5, %bb2 ]
+  %i4 = tail call signext i32 @bar(i32 signext %i3)
+  %i5 = shl i32 %i3, %arg1
+  %i6 = icmp eq i32 %i4, 0
+  br i1 %i6, label %bb7, label %bb2
+
+bb7:                                              ; preds = %bb2
+  ret void
+}
+
+define void @test17(i32 signext %arg, i32 signext %arg1) nounwind {
+; CHECK-LABEL: test17:
+; CHECK:       # %bb.0: # %bb
+; CHECK-NEXT:    addi sp, sp, -32
+; CHECK-NEXT:    sd ra, 24(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    sd s0, 16(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    sd s1, 8(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    mv s0, a1
+; CHECK-NEXT:    call bat@plt
+; CHECK-NEXT:    mv s1, a0
+; CHECK-NEXT:  .LBB20_1: # %bb2
+; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    mv a0, s1
+; CHECK-NEXT:    call bar@plt
+; CHECK-NEXT:    sllw s1, s1, s0
+; CHECK-NEXT:    bnez a0, .LBB20_1
+; CHECK-NEXT:  # %bb.2: # %bb7
+; CHECK-NEXT:    ld ra, 24(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    ld s0, 16(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    ld s1, 8(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    addi sp, sp, 32
+; CHECK-NEXT:    ret
+;
+; NOREMOVAL-LABEL: test17:
+; NOREMOVAL:       # %bb.0: # %bb
+; NOREMOVAL-NEXT:    addi sp, sp, -32
+; NOREMOVAL-NEXT:    sd ra, 24(sp) # 8-byte Folded Spill
+; NOREMOVAL-NEXT:    sd s0, 16(sp) # 8-byte Folded Spill
+; NOREMOVAL-NEXT:    sd s1, 8(sp) # 8-byte Folded Spill
+; NOREMOVAL-NEXT:    mv s0, a1
+; NOREMOVAL-NEXT:    call bat@plt
+; NOREMOVAL-NEXT:    mv s1, a0
+; NOREMOVAL-NEXT:  .LBB20_1: # %bb2
+; NOREMOVAL-NEXT:    # =>This Inner Loop Header: Depth=1
+; NOREMOVAL-NEXT:    sext.w a0, s1
+; NOREMOVAL-NEXT:    call bar@plt
+; NOREMOVAL-NEXT:    sllw s1, s1, s0
+; NOREMOVAL-NEXT:    bnez a0, .LBB20_1
+; NOREMOVAL-NEXT:  # %bb.2: # %bb7
+; NOREMOVAL-NEXT:    ld ra, 24(sp) # 8-byte Folded Reload
+; NOREMOVAL-NEXT:    ld s0, 16(sp) # 8-byte Folded Reload
+; NOREMOVAL-NEXT:    ld s1, 8(sp) # 8-byte Folded Reload
+; NOREMOVAL-NEXT:    addi sp, sp, 32
+; NOREMOVAL-NEXT:    ret
+bb:
+  %i = call zeroext i16 @bat(i32 signext %arg)
+  %zext = zext i16 %i to i32
+  br label %bb2
+
+bb2:                                              ; preds = %bb2, %bb
+  %i3 = phi i32 [ %zext, %bb ], [ %i5, %bb2 ]
+  %i4 = tail call signext i32 @bar(i32 signext %i3)
+  %i5 = shl i32 %i3, %arg1
+  %i6 = icmp eq i32 %i4, 0
+  br i1 %i6, label %bb7, label %bb2
+
+bb7:                                              ; preds = %bb2
+  ret void
+}
+declare zeroext i16 @bat(i32 signext)