[llvm] r296768 - [DAGCombiner] avoid assertion when folding binops with opaque constants

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Thu Mar  2 11:18:56 2017
New Revision: 296768

URL: http://llvm.org/viewvc/llvm-project?rev=296768&view=rev
Log:
[DAGCombiner] avoid assertion when folding binops with opaque constants

This bug was introduced with:
https://reviews.llvm.org/rL296699

There may be a way to loosen the restriction, but for now just bail out
on any opaque constant.

The tests show that opacity is target-specific. This goes back to cost
calculations in ConstantHoisting based on TTI->getIntImmCost().

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/test/CodeGen/ARM/select_const.ll
    llvm/trunk/test/CodeGen/X86/select_const.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=296768&r1=296767&r2=296768&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Mar  2 11:18:56 2017
@@ -1761,8 +1761,9 @@ SDValue DAGCombiner::foldBinOpIntoSelect
           BinOpcode == ISD::FDIV || BinOpcode == ISD::FREM) &&
          "Unexpected binary operator");
 
+  // Bail out if any constants are opaque because we can't constant fold those.
   SDValue C1 = BO->getOperand(1);
-  if (!isConstantOrConstantVector(C1) &&
+  if (!isConstantOrConstantVector(C1, true) &&
       !isConstantFPBuildVectorOrConstantFP(C1))
     return SDValue();
 
@@ -1774,12 +1775,12 @@ SDValue DAGCombiner::foldBinOpIntoSelect
     return SDValue();
 
   SDValue CT = Sel.getOperand(1);
-  if (!isConstantOrConstantVector(CT) &&
+  if (!isConstantOrConstantVector(CT, true) &&
       !isConstantFPBuildVectorOrConstantFP(CT))
     return SDValue();
 
   SDValue CF = Sel.getOperand(2);
-  if (!isConstantOrConstantVector(CF) &&
+  if (!isConstantOrConstantVector(CF, true) &&
       !isConstantFPBuildVectorOrConstantFP(CF))
     return SDValue();
 

Modified: llvm/trunk/test/CodeGen/ARM/select_const.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/select_const.ll?rev=296768&r1=296767&r2=296768&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/select_const.ll (original)
+++ llvm/trunk/test/CodeGen/ARM/select_const.ll Thu Mar  2 11:18:56 2017
@@ -273,3 +273,54 @@ define i32 @select_C1_C2_signext(i1 sign
   ret i32 %sel
 }
 
+; 4295032833 = 0x100010001.
+; This becomes an opaque constant via ConstantHoisting, so we don't fold it into the select.
+
+define i64 @opaque_constant1(i1 %cond, i64 %x) {
+; CHECK-LABEL: opaque_constant1:
+; CHECK:       @ BB#0:
+; CHECK-NEXT:    .save {r4, lr}
+; CHECK-NEXT:    push {r4, lr}
+; CHECK-NEXT:    ands r12, r0, #1
+; CHECK-NEXT:    mov lr, #1
+; CHECK-NEXT:    mov r0, #23
+; CHECK-NEXT:    eor r3, r3, #1
+; CHECK-NEXT:    orr lr, lr, #65536
+; CHECK-NEXT:    mvnne r0, #3
+; CHECK-NEXT:    movne r12, #1
+; CHECK-NEXT:    and r4, r0, lr
+; CHECK-NEXT:    eor r2, r2, lr
+; CHECK-NEXT:    subs r0, r4, #1
+; CHECK-NEXT:    sbc r1, r12, #0
+; CHECK-NEXT:    orrs r2, r2, r3
+; CHECK-NEXT:    movne r0, r4
+; CHECK-NEXT:    movne r1, r12
+; CHECK-NEXT:    pop {r4, lr}
+; CHECK-NEXT:    mov pc, lr
+  %sel = select i1 %cond, i64 -4, i64 23
+  %bo = and i64 %sel, 4295032833  ; 0x100010001
+  %cmp = icmp eq i64 %x, 4295032833
+  %sext = sext i1 %cmp to i64
+  %add = add i64 %bo, %sext
+  ret i64 %add
+}
+
+; 65537 == 0x10001.
+; This becomes an opaque constant via ConstantHoisting, so we don't fold it into the select.
+
+define i64 @opaque_constant2(i1 %cond, i64 %x) {
+; CHECK-LABEL: opaque_constant2:
+; CHECK:       @ BB#0:
+; CHECK-NEXT:    mov r1, #1
+; CHECK-NEXT:    tst r0, #1
+; CHECK-NEXT:    orr r1, r1, #65536
+; CHECK-NEXT:    mov r0, r1
+; CHECK-NEXT:    moveq r0, #23
+; CHECK-NEXT:    and r0, r0, r1
+; CHECK-NEXT:    mov r1, #0
+; CHECK-NEXT:    mov pc, lr
+  %sel = select i1 %cond, i64 65537, i64 23
+  %bo = and i64 %sel, 65537
+  ret i64 %bo
+}
+

Modified: llvm/trunk/test/CodeGen/X86/select_const.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/select_const.ll?rev=296768&r1=296767&r2=296768&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/select_const.ll (original)
+++ llvm/trunk/test/CodeGen/X86/select_const.ll Thu Mar  2 11:18:56 2017
@@ -291,3 +291,29 @@ define <2 x double> @sel_constants_fmul_
   %bo = fmul <2 x double> %sel, <double 5.1, double 3.14>
   ret <2 x double> %bo
 }
+
+; 4294967297 = 0x100000001.
+; This becomes an opaque constant via ConstantHoisting, so we don't fold it into the select.
+
+define i64 @opaque_constant(i1 %cond, i64 %x) {
+; CHECK-LABEL: opaque_constant:
+; CHECK:       # BB#0:
+; CHECK-NEXT:    testb $1, %dil
+; CHECK-NEXT:    movl $23, %ecx
+; CHECK-NEXT:    movq $-4, %rax
+; CHECK-NEXT:    cmoveq %rcx, %rax
+; CHECK-NEXT:    movabsq $4294967297, %rcx # imm = 0x100000001
+; CHECK-NEXT:    andq %rcx, %rax
+; CHECK-NEXT:    xorl %edx, %edx
+; CHECK-NEXT:    cmpq %rcx, %rsi
+; CHECK-NEXT:    sete %dl
+; CHECK-NEXT:    subq %rdx, %rax
+; CHECK-NEXT:    retq
+  %sel = select i1 %cond, i64 -4, i64 23
+  %bo = and i64 %sel, 4294967297
+  %cmp = icmp eq i64 %x, 4294967297
+  %sext = sext i1 %cmp to i64
+  %add = add i64 %bo, %sext
+  ret i64 %add
+}
+