[SelectionDAG] Compute known bits of CopyFromReg

Summary:
Teach SelectionDAG how to compute known bits of ISD::CopyFromReg if
the virtual reg used has one def only.

This can be particularly useful when calling isBaseWithConstantOffset()
with the ISD::CopyFromReg argument, as more optimizations may get enabled
in the result.

Also add a missing truncation on X86, found by testing of this patch.

Change-Id: Id1c9fceec862d118c54a5b53adf72ada5d6daefa

Reviewers: bogner, craig.topper, RKSimon

Reviewed By: RKSimon

Subscribers: lebedev.ri, nemanjai, jvesely, nhaehnle, javed.absar, jsji, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59535

llvm-svn: 357745

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -31,6 +31,7 @@
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineMemOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/RuntimeLibcalls.h"
 #include "llvm/CodeGen/SelectionDAGAddressAnalysis.h"
 #include "llvm/CodeGen/SelectionDAGNodes.h"
@@ -3202,6 +3203,25 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
     Known.One &= Known2.One;
     break;
   }
+  case ISD::CopyFromReg: {
+    auto R = cast<RegisterSDNode>(Op.getOperand(1));
+    const unsigned Reg = R->getReg();
+
+    const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
+    if (!TRI->isVirtualRegister(Reg))
+      break;
+
+    const MachineRegisterInfo *MRI = &MF->getRegInfo();
+    if (!MRI->hasOneDef(Reg))
+      break;
+
+    const FunctionLoweringInfo::LiveOutInfo *LOI = FLI->GetLiveOutRegInfo(Reg);
+    if (!LOI || LOI->Known.getBitWidth() != BitWidth)
+      break;
+
+    Known = LOI->Known;
+    break;
+  }
   case ISD::FrameIndex:
   case ISD::TargetFrameIndex:
     TLI->computeKnownBitsForFrameIndex(Op, Known, DemandedElts, *this, Depth);

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -19580,10 +19580,10 @@ static SDValue LowerAndToBT(SDValue And, ISD::CondCode CC,
       DAG.MaskedValueIsZero(BitNo, APInt(BitNo.getValueSizeInBits(), 32)))
     Src = DAG.getNode(ISD::TRUNCATE, dl, MVT::i32, Src);
 
-  // If the operand types disagree, extend the shift amount to match.  Since
-  // BT ignores high bits (like shifts) we can use anyextend.
+  // If the operand types disagree, extend or truncate the shift amount to match.
+  // Since BT ignores high bits (like shifts) we can use anyextend for the extension.
   if (Src.getValueType() != BitNo.getValueType())
-    BitNo = DAG.getNode(ISD::ANY_EXTEND, dl, Src.getValueType(), BitNo);
+    BitNo = DAG.getAnyExtOrTrunc(BitNo, dl, Src.getValueType());
 
   X86CC = DAG.getConstant(CC == ISD::SETEQ ? X86::COND_AE : X86::COND_B,
                           dl, MVT::i8);

llvm/test/CodeGen/AMDGPU/llvm.amdgcn.s.buffer.load.ll

@@ -110,8 +110,8 @@ main_body:
 
 ;CHECK-LABEL: {{^}}s_buffer_load_index_across_bb:
 ;CHECK-NOT: s_waitcnt;
-;CHECK: v_or_b32
-;CHECK: buffer_load_dword v{{[0-9]+}}, v{{[0-9]+}}, s[{{[0-9]+:[0-9]+}}], 0 offen
+;CHECK-NOT: v_or_b32
+;CHECK: buffer_load_dword v{{[0-9]+}}, v{{[0-9]+}}, s[{{[0-9]+:[0-9]+}}], 0 offen offset:8
 define amdgpu_ps void @s_buffer_load_index_across_bb(<4 x i32> inreg %desc, i32 %index) {
 main_body:
   %tmp = shl i32 %index, 4
@@ -127,10 +127,8 @@ bb1:                                              ; preds = %main_body
 
 ;CHECK-LABEL: {{^}}s_buffer_load_index_across_bb_merged:
 ;CHECK-NOT: s_waitcnt;
-;CHECK: v_or_b32
-;CHECK: v_or_b32
-;CHECK: buffer_load_dword v{{[0-9]+}}, v{{[0-9]+}}, s[{{[0-9]+:[0-9]+}}], 0 offen
-;CHECK: buffer_load_dword v{{[0-9]+}}, v{{[0-9]+}}, s[{{[0-9]+:[0-9]+}}], 0 offen
+;CHECK-NOT: v_or_b32
+;CHECK: buffer_load_dwordx2 v[{{[0-9]+:[0-9]+}}], v{{[0-9]+}}, s[{{[0-9]+:[0-9]+}}], 0 offen offset:8
 define amdgpu_ps void @s_buffer_load_index_across_bb_merged(<4 x i32> inreg %desc, i32 %index) {
 main_body:
   %tmp = shl i32 %index, 4

llvm/test/CodeGen/ARM/atomic-op.ll

@@ -183,11 +183,11 @@ entry:
   ret void
 }
 
-define void @func2() nounwind {
+define void @func2(i16 %int_val) nounwind {
 entry:
   %val = alloca i16
   %old = alloca i16
-  store i16 31, i16* %val
+  store i16 %int_val, i16* %val
   ; CHECK: ldrex
   ; CHECK: cmp
   ; CHECK: strex
@@ -197,7 +197,7 @@ entry:
   ; CHECK-BAREMETAL-NOT: __sync
   %0 = atomicrmw umin i16* %val, i16 16 monotonic
   store i16 %0, i16* %old
-  %uneg = sub i16 0, 1
+  %uneg = sub i16 0, 2
   ; CHECK: ldrex
   ; CHECK: cmp
   ; CHECK: strex
@@ -249,7 +249,7 @@ entry:
   ; CHECK-T1-M0: bl ___sync_fetch_and_umin_1
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
-  %uneg = sub i8 0, 1
+  %uneg = sub i8 0, 2
   %1 = atomicrmw umin i8* %val, i8 %uneg monotonic
   store i8 %1, i8* %old
   ; CHECK: ldrex

llvm/test/CodeGen/PowerPC/pr35688.ll

@@ -6,16 +6,14 @@
 ; Function Attrs: nounwind
 define void @ec_GFp_nistp256_points_mul() {
 ; CHECK-LABEL: ec_GFp_nistp256_points_mul:
-; CHECK:    ld 5, 0(3)
-; CHECK:    li 3, 127
-; CHECK:    li 4, 0
-; CHECK:    subfic 6, 5, 0
-; CHECK:    subfze 6, 4
-; CHECK:    sradi 7, 6, 63
-; CHECK:    srad 6, 6, 3
-; CHECK:    subfc 5, 5, 7
-; CHECK:    subfe 5, 4, 6
+; CHECK:    ld 4, 0(3)
+; CHECK:    li 3, 0
+; CHECK:    subfic 5, 4, 0
+; CHECK:    subfze 5, 3
 ; CHECK:    sradi 5, 5, 63
+; CHECK:    subfc 4, 4, 5
+; CHECK:    subfe 4, 3, 5
+; CHECK:    sradi 4, 4, 63
 
 ; With MemorySSA, everything is taken out of the loop by licm.
 ; Loads and stores to undef are treated as non-aliasing.

llvm/test/CodeGen/SystemZ/subregliveness-04.ll

@@ -1,7 +1,7 @@
 ; RUN: llc -mtriple=s390x-linux-gnu -mcpu=z13 -disable-early-taildup -disable-cgp -systemz-subreg-liveness < %s | FileCheck %s
 
 ; Check for successful compilation.
-; CHECK: lhi %r0, -5
+; CHECK: lhi {{%r[0-9]+}}, -5
 
 target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64"
 target triple = "s390x-ibm-linux"

llvm/test/CodeGen/X86/fold-tied-op.ll

@@ -6,8 +6,8 @@ target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128"
 target triple = "i386--netbsd"
 
 ; CHECK-LABEL: fn1
-; CHECK:       orl  {{.*#+}} 4-byte Folded Reload
 ; CHECK:       addl {{.*#+}} 4-byte Folded Reload
+; CHECK:       orl  {{.*#+}} 4-byte Folded Reload
 ; CHECK:       xorl {{.*#+}} 4-byte Folded Reload
 ; CHECK:       xorl {{.*#+}} 4-byte Folded Reload
 ; CHECK:       retl

llvm/test/CodeGen/X86/pr28444.ll

@@ -11,9 +11,8 @@
 define void @extractelt_mismatch_vector_element_type(i32 %arg, i1 %x) {
 ; CHECK-LABEL: extractelt_mismatch_vector_element_type:
 ; CHECK:       # %bb.0: # %bb
-; CHECK-NEXT:    movb $1, %al
-; CHECK-NEXT:    movb %al, (%rax)
-; CHECK-NEXT:    movb %al, (%rax)
+; CHECK-NEXT:    movb $1, (%rax)
+; CHECK-NEXT:    movb $1, (%rax)
 ; CHECK-NEXT:    retq
 bb:
   %tmp = icmp ult i32 %arg, 0