ARM assembly 'cmp lr, #0' should not encode using 'cmn'.

The CMP->CMN alias was matching for an immediate of zero when it
should only match for negative values.

rdar://11129224

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153689 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 10 insertions, 4 deletions

diff --git a/lib/Target/ARM/ARMInstrInfo.td b/lib/Target/ARM/ARMInstrInfo.td
index 784a028db4..c0bd237f2e 100644
--- a/lib/Target/ARM/ARMInstrInfo.td
+++ b/lib/Target/ARM/ARMInstrInfo.td
@@ -251,7 +251,8 @@ def imm16_31 : ImmLeaf<i32, [{
 
 def so_imm_neg_asmoperand : AsmOperandClass { let Name = "ARMSOImmNeg"; }
 def so_imm_neg : Operand<i32>, PatLeaf<(imm), [{
-    return ARM_AM::getSOImmVal(-(uint32_t)N->getZExtValue()) != -1;
+    int64_t Value = -(int)N->getZExtValue();
+    return Value && ARM_AM::getSOImmVal(Value) != -1;
   }], so_imm_neg_XFORM> {
   let ParserMatchClass = so_imm_neg_asmoperand;
 }
diff --git a/lib/Target/ARM/ARMInstrThumb2.td b/lib/Target/ARM/ARMInstrThumb2.td
index 1f7edc1aaf..63d3a63c73 100644
--- a/lib/Target/ARM/ARMInstrThumb2.td
+++ b/lib/Target/ARM/ARMInstrThumb2.td
@@ -89,7 +89,8 @@ def t2_so_imm_not : Operand<i32>, PatLeaf<(imm), [{
 // t2_so_imm_neg - Match an immediate that is a negation of a t2_so_imm.
 def t2_so_imm_neg_asmoperand : AsmOperandClass { let Name = "T2SOImmNeg"; }
 def t2_so_imm_neg : Operand<i32>, PatLeaf<(imm), [{
-  return ARM_AM::getT2SOImmVal(-((uint32_t)N->getZExtValue())) != -1;
+  int64_t Value = -(int)N->getZExtValue();
+  return Value && ARM_AM::getT2SOImmVal(Value) != -1;
 }], t2_so_imm_neg_XFORM> {
   let ParserMatchClass = t2_so_imm_neg_asmoperand;
 }
diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 911eb132e5..e0022064ba 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -782,7 +782,8 @@ public:
     const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
     if (!CE) return false;
     int64_t Value = CE->getValue();
-    return ARM_AM::getSOImmVal(-Value) != -1;
+    // Negation must be representable as an so_imm and be non-zero.
+    return Value && ARM_AM::getSOImmVal(-Value) != -1;
   }
   bool isT2SOImm() const {
     if (!isImm()) return false;
@@ -803,7 +804,8 @@ public:
     const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
     if (!CE) return false;
     int64_t Value = CE->getValue();
-    return ARM_AM::getT2SOImmVal(-Value) != -1;
+    // Negation must be representable as a t2_so_imm and be non-zero.
+    return Value && ARM_AM::getT2SOImmVal(-Value) != -1;
   }
   bool isSetEndImm() const {
     if (!isImm()) return false;
diff --git a/test/MC/ARM/basic-arm-instructions.s b/test/MC/ARM/basic-arm-instructions.s
index 4ae1ac76f3..1e09e4e8eb 100644
--- a/test/MC/ARM/basic-arm-instructions.s
+++ b/test/MC/ARM/basic-arm-instructions.s
@@ -494,6 +494,7 @@ Lforward:
         cmp r7, r8, ror r2
         cmp r1, r6, rrx
         cmp r0, #-2
+        cmp lr, #0
 
 @ CHECK: cmp	r1, #15                 @ encoding: [0x0f,0x00,0x51,0xe3]
 @ CHECK: cmp	r1, r6                  @ encoding: [0x06,0x00,0x51,0xe1]
@@ -508,6 +509,7 @@ Lforward:
 @ CHECK: cmp	r7, r8, ror r2          @ encoding: [0x78,0x02,0x57,0xe1]
 @ CHECK: cmp	r1, r6, rrx             @ encoding: [0x66,0x00,0x51,0xe1]
 @ CHECK: cmn	r0, #2                  @ encoding: [0x02,0x00,0x70,0xe3]
+@ CHECK: cmp  lr, #0                    @ encoding: [0x00,0x00,0x5e,0xe3]
 
 
 @------------------------------------------------------------------------------