[llvm] r177687 - Fix the invalid opcode for Mips branch instructions in the assembler

[Jack Carter]

Author: jacksprat
Date: Thu Mar 21 19:29:10 2013
New Revision: 177687

URL: http://llvm.org/viewvc/llvm-project?rev=177687&view=rev
Log:
Fix the invalid opcode for Mips branch instructions in the assembler

For mips a branch an 18-bit signed offset (the 16-bit 
offset field shifted left 2 bits) is added to the 
address of the instruction following the branch 
(not the branch itself), in the branch delay slot, 
to form a PC-relative effective target address. 

Previously, the code generator did not perform the 
shift of the immediate branch offset which resulted 
in wrong instruction opcode. This patch fixes the issue.

Contributor: Vladimir Medic


Modified:
    llvm/trunk/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
    llvm/trunk/test/MC/Mips/mips-jump-instructions.s

Modified: llvm/trunk/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp?rev=177687&r1=177686&r2=177687&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp (original)
+++ llvm/trunk/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp Thu Mar 21 19:29:10 2013
@@ -160,8 +160,9 @@ getBranchTargetOpValue(const MCInst &MI,
 
   const MCOperand &MO = MI.getOperand(OpNo);
 
-  // If the destination is an immediate, we have nothing to do.
-  if (MO.isImm()) return MO.getImm();
+  // If the destination is an immediate, divide by 4.
+  if (MO.isImm()) return MO.getImm() >> 2;
+
   assert(MO.isExpr() &&
          "getBranchTargetOpValue expects only expressions or immediates");
 
@@ -179,8 +180,9 @@ getJumpTargetOpValue(const MCInst &MI, u
                      SmallVectorImpl<MCFixup> &Fixups) const {
 
   const MCOperand &MO = MI.getOperand(OpNo);
-  // If the destination is an immediate, we have nothing to do.
-  if (MO.isImm()) return MO.getImm();
+  // If the destination is an immediate, divide by 4.
+  if (MO.isImm()) return MO.getImm()>>2;
+
   assert(MO.isExpr() &&
          "getJumpTargetOpValue expects only expressions or an immediate");
 

Modified: llvm/trunk/test/MC/Mips/mips-jump-instructions.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/Mips/mips-jump-instructions.s?rev=177687&r1=177686&r2=177687&view=diff
==============================================================================
--- llvm/trunk/test/MC/Mips/mips-jump-instructions.s (original)
+++ llvm/trunk/test/MC/Mips/mips-jump-instructions.s Thu Mar 21 19:29:10 2013
@@ -5,25 +5,25 @@
 #------------------------------------------------------------------------------
 # Branch instructions
 #------------------------------------------------------------------------------
-# CHECK:   b 1332                 # encoding: [0x34,0x05,0x00,0x10]
+# CHECK:   b 1332                 # encoding: [0x4d,0x01,0x00,0x10]
 # CHECK:   nop                    # encoding: [0x00,0x00,0x00,0x00]
-# CHECK:   bc1f 1332              # encoding: [0x34,0x05,0x00,0x45]
+# CHECK:   bc1f 1332              # encoding: [0x4d,0x01,0x00,0x45]
 # CHECK:   nop                    # encoding: [0x00,0x00,0x00,0x00]
-# CHECK:   bc1t 1332              # encoding: [0x34,0x05,0x01,0x45]
+# CHECK:   bc1t 1332              # encoding: [0x4d,0x01,0x01,0x45]
 # CHECK:   nop                    # encoding: [0x00,0x00,0x00,0x00]
-# CHECK:   beq $9, $6, 1332       # encoding: [0x34,0x05,0x26,0x11]
+# CHECK:   beq $9, $6, 1332       # encoding: [0x4d,0x01,0x26,0x11]
 # CHECK:   nop                    # encoding: [0x00,0x00,0x00,0x00]
-# CHECK:   bgez $6, 1332          # encoding: [0x34,0x05,0xc1,0x04]
+# CHECK:   bgez $6, 1332          # encoding: [0x4d,0x01,0xc1,0x04]
 # CHECK:   nop                    # encoding: [0x00,0x00,0x00,0x00]
-# CHECK:   bgezal $6, 1332        # encoding: [0x34,0x05,0xd1,0x04]
+# CHECK:   bgezal $6, 1332        # encoding: [0x4d,0x01,0xd1,0x04]
 # CHECK:   nop                    # encoding: [0x00,0x00,0x00,0x00]
-# CHECK:   bgtz $6, 1332          # encoding: [0x34,0x05,0xc0,0x1c]
+# CHECK:   bgtz $6, 1332          # encoding: [0x4d,0x01,0xc0,0x1c]
 # CHECK:   nop                    # encoding: [0x00,0x00,0x00,0x00]
-# CHECK:   blez $6, 1332          # encoding: [0x34,0x05,0xc0,0x18]
+# CHECK:   blez $6, 1332          # encoding: [0x4d,0x01,0xc0,0x18]
 # CHECK:   nop                    # encoding: [0x00,0x00,0x00,0x00]
-# CHECK:   bne $9, $6, 1332       # encoding: [0x34,0x05,0x26,0x15]
+# CHECK:   bne $9, $6, 1332       # encoding: [0x4d,0x01,0x26,0x15]
 # CHECK:   nop                    # encoding: [0x00,0x00,0x00,0x00]
-# CHECK:   bal     1332           # encoding: [0x34,0x05,0x11,0x04]
+# CHECK:   bal     1332           # encoding: [0x4d,0x01,0x11,0x04]
 # CHECK:   nop                    # encoding: [0x00,0x00,0x00,0x00]
          b 1332
          nop
@@ -50,9 +50,9 @@ end_of_code:
 #------------------------------------------------------------------------------
 # Jump instructions
 #------------------------------------------------------------------------------
-# CHECK:   j 1328               # encoding: [0x30,0x05,0x00,0x08]
+# CHECK:   j 1328               # encoding: [0x4c,0x01,0x00,0x08]
 # CHECK:   nop                  # encoding: [0x00,0x00,0x00,0x00]
-# CHECK:   jal 1328             # encoding: [0x30,0x05,0x00,0x0c]
+# CHECK:   jal 1328             # encoding: [0x4c,0x01,0x00,0x0c]
 # CHECK:   nop                  # encoding: [0x00,0x00,0x00,0x00]
 # CHECK:   jalr $6              # encoding: [0x09,0xf8,0xc0,0x00]
 # CHECK:   nop                  # encoding: [0x00,0x00,0x00,0x00]