Brian Gaeke says:

lib/Target/X86/InstSelectSimple.cpp: Add a little something to
 visitBranchInst which supports conditional branches.
lib/Target/X86/X86InstrInfo.def: Add defs of JNE, JE, CMPri8


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4755 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 43 insertions, 12 deletions

diff --git a/lib/Target/X86/InstSelectSimple.cpp b/lib/Target/X86/InstSelectSimple.cpp
index d74bfd4912..f0ffc679ed 100644
--- a/lib/Target/X86/InstSelectSimple.cpp
+++ b/lib/Target/X86/InstSelectSimple.cpp
@@ -386,17 +386,31 @@ void ISel::visitReturnInst (ReturnInst &I) {
   BuildMI(BB, X86::RET, 0);
 }
 
-
 /// visitBranchInst - Handle conditional and unconditional branches here.  Note
 /// that since code layout is frozen at this point, that if we are trying to
 /// jump to a block that is the immediate successor of the current block, we can
 /// just make a fall-through. (but we don't currently).
 ///
-void ISel::visitBranchInst(BranchInst &BI) {
-  if (BI.isConditional())   // Only handles unconditional branches so far...
-    visitInstruction(BI);
-
-  BuildMI(BB, X86::JMP, 1).addPCDisp(BI.getSuccessor(0));
+void
+ISel::visitBranchInst (BranchInst & BI)
+{
+  if (BI.isConditional ())
+    {
+      BasicBlock *ifTrue = BI.getSuccessor (0);
+      BasicBlock *ifFalse = BI.getSuccessor (1); // this is really unobvious 
+
+      // simplest thing I can think of: compare condition with zero,
+      // followed by jump-if-equal to ifFalse, and jump-if-nonequal to
+      // ifTrue
+      unsigned int condReg = getReg (BI.getCondition ());
+      BuildMI (BB, X86::CMPri8, 2, X86::EFLAGS).addReg (condReg).addZImm (0);
+      BuildMI (BB, X86::JNE, 1).addPCDisp (BI.getSuccessor (0));
+      BuildMI (BB, X86::JE, 1).addPCDisp (BI.getSuccessor (1));
+    }
+  else // unconditional branch
+    {
+      BuildMI (BB, X86::JMP, 1).addPCDisp (BI.getSuccessor (0));
+    }
 }
 
 
diff --git a/lib/Target/X86/X86ISelSimple.cpp b/lib/Target/X86/X86ISelSimple.cpp
index d74bfd4912..f0ffc679ed 100644
--- a/lib/Target/X86/X86ISelSimple.cpp
+++ b/lib/Target/X86/X86ISelSimple.cpp
@@ -386,17 +386,31 @@ void ISel::visitReturnInst (ReturnInst &I) {
   BuildMI(BB, X86::RET, 0);
 }
 
-
 /// visitBranchInst - Handle conditional and unconditional branches here.  Note
 /// that since code layout is frozen at this point, that if we are trying to
 /// jump to a block that is the immediate successor of the current block, we can
 /// just make a fall-through. (but we don't currently).
 ///
-void ISel::visitBranchInst(BranchInst &BI) {
-  if (BI.isConditional())   // Only handles unconditional branches so far...
-    visitInstruction(BI);
-
-  BuildMI(BB, X86::JMP, 1).addPCDisp(BI.getSuccessor(0));
+void
+ISel::visitBranchInst (BranchInst & BI)
+{
+  if (BI.isConditional ())
+    {
+      BasicBlock *ifTrue = BI.getSuccessor (0);
+      BasicBlock *ifFalse = BI.getSuccessor (1); // this is really unobvious 
+
+      // simplest thing I can think of: compare condition with zero,
+      // followed by jump-if-equal to ifFalse, and jump-if-nonequal to
+      // ifTrue
+      unsigned int condReg = getReg (BI.getCondition ());
+      BuildMI (BB, X86::CMPri8, 2, X86::EFLAGS).addReg (condReg).addZImm (0);
+      BuildMI (BB, X86::JNE, 1).addPCDisp (BI.getSuccessor (0));
+      BuildMI (BB, X86::JE, 1).addPCDisp (BI.getSuccessor (1));
+    }
+  else // unconditional branch
+    {
+      BuildMI (BB, X86::JMP, 1).addPCDisp (BI.getSuccessor (0));
+    }
 }
 
 
diff --git a/lib/Target/X86/X86InstrInfo.def b/lib/Target/X86/X86InstrInfo.def
index 69c6178b30..27605d79ad 100644
--- a/lib/Target/X86/X86InstrInfo.def
+++ b/lib/Target/X86/X86InstrInfo.def
@@ -37,6 +37,8 @@ I(NOOP        , "nop",   0x90,             0, X86II::RawFrm | X86II::Void) // no
 // Flow control instructions
 I(RET         , "ret",   0xCB,    M_RET_FLAG, X86II::RawFrm | X86II::Void) // ret
 I(JMP         , "jmp",   0x00, M_BRANCH_FLAG, X86II::Void) // jmp foo      EB|E9 cb|w
+I(JNE         , "jne",   0x00, M_BRANCH_FLAG, X86II::Void) // 75 cb, or 0f 85 cw|cd
+I(JE         , "je",   0x00, M_BRANCH_FLAG, X86II::Void) // 74 cb, or 0f 84 cw|cd
 
 // Misc instructions
 I(LEAVE       , "leave", 0xC9,             0, X86II::RawFrm)                   // leave
@@ -134,6 +136,7 @@ I(SETNE       , "setne", 0x95,             0, X86II::TB)   // R8 = !=       0F 9
 I(CMPrr8      , "cmpb",  0x38,             0, X86II::MRMDestReg)               // compare R8,R8   38/r
 I(CMPrr16     , "cmpw",  0x39,             0, X86II::MRMDestReg)               // compare R16,R16 39/r
 I(CMPrr32     , "cmpl",  0x39,             0, X86II::MRMDestReg)               // compare R32,R32 39/r
+I(CMPri8      , "cmp",   0x80,             0, 0)                               // compare R8, imm8 80 /7 ib
 
 // Sign extenders (first 3 are good for DIV/IDIV; the others are more general)
 I(CBW         , "cbw",   0x98,             0, X86II::RawFrm)     // AX = signext(AL)