[llvm] c351050 - [ARM] support symbolic expressions as branch target in b.w

[Jian Cai via llvm-commits]

Author: Jian Cai
Date: 2021-03-01T17:41:35-08:00
New Revision: c35105055ee4565ee6726d5b155538dd5c0307d3

URL: https://github.com/llvm/llvm-project/commit/c35105055ee4565ee6726d5b155538dd5c0307d3
DIFF: https://github.com/llvm/llvm-project/commit/c35105055ee4565ee6726d5b155538dd5c0307d3.diff

LOG: [ARM] support symbolic expressions as branch target in b.w

Currently ARM backend validates the range of branch targets before the
layout of fragments is finalized. This causes build failure if symbolic
expressions are used, with the exception of a single symbolic value.
For example, "b.w ." works but "b.w . + 2" currently fails to
assemble. This fixes the issue by delaying this check (in
ARMAsmParser::validateInstruction) of b.w instructions until the symbol
expressions are resolved (in ARMAsmBackend::adjustFixupValue).

Link:
https://github.com/ClangBuiltLinux/linux/issues/1286

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D97568

Added: 
    llvm/test/MC/ARM/thumb2-b.w-target.s

Modified: 
    llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
    llvm/test/MC/ARM/thumb2-branch-ranges.s

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index b64637cfb37b..9a2d94e3972c 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -7950,7 +7950,10 @@ bool ARMAsmParser::validateInstruction(MCInst &Inst,
     break;
   case ARM::t2B: {
     int op = (Operands[2]->isImm()) ? 2 : 3;
-    if (!static_cast<ARMOperand &>(*Operands[op]).isSignedOffset<24, 1>())
+    ARMOperand &Operand = static_cast<ARMOperand &>(*Operands[op]);
+    // Delay the checks of symbolic expressions until they are resolved.
+    if (!isa<MCBinaryExpr>(Operand.getImm()) &&
+        !Operand.isSignedOffset<24, 1>())
       return Error(Operands[op]->getStartLoc(), "branch target out of range");
     break;
   }

diff  --git a/llvm/test/MC/ARM/thumb2-b.w-target.s b/llvm/test/MC/ARM/thumb2-b.w-target.s
new file mode 100644
index 000000000000..1323730552f0
--- /dev/null
+++ b/llvm/test/MC/ARM/thumb2-b.w-target.s
@@ -0,0 +1,12 @@
+// RUN: llvm-mc -triple=thumbv7 -filetype=obj %s | llvm-objdump --triple=thumbv7 -d - | FileCheck %s
+
+.syntax unified
+
+// CHECK-LABEL: start
+// CHECK-NEXT:	b.w	#16777208
+// CHECK-NEXT:  b.w	#2
+start:
+  b.w start - 1f + 0x1000000
+1:
+  b.w . + (2f - 1b + 2)
+2:

diff  --git a/llvm/test/MC/ARM/thumb2-branch-ranges.s b/llvm/test/MC/ARM/thumb2-branch-ranges.s
index 6f537d85b449..83cb0259d741 100644
--- a/llvm/test/MC/ARM/thumb2-branch-ranges.s
+++ b/llvm/test/MC/ARM/thumb2-branch-ranges.s
@@ -94,3 +94,9 @@ start6:
 // CHECK: [[@LINE+2]]:{{[0-9]}}: error: Relocation out of range
 // CHECK-LABEL: beq.w start6
         beq.w start6
+
+start7:
+// branch to thumb function resolved at assembly time
+// CHECK: [[#@LINE+1]]:{{[0-9]}}: error: Relocation out of range
+        b.w start8 - start7 + 0x1000000
+start8: