From 6d64b3adab682aea9c0b4dd665acc5e863ac6d21 Mon Sep 17 00:00:00 2001
From: Chad Rosier <mcrosier@apple.com>
Date: Thu, 27 Oct 2011 00:21:16 +0000
Subject: [PATCH] A branch predicated on a constant can just FastEmit an
 unconditional branch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143086 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMFastISel.cpp         |  6 ++++
 test/CodeGen/ARM/fast-isel-br-const.ll | 47 ++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 test/CodeGen/ARM/fast-isel-br-const.ll

diff --git a/lib/Target/ARM/ARMFastISel.cpp b/lib/Target/ARM/ARMFastISel.cpp
index a67c8671458..6aff834b954 100644
--- a/lib/Target/ARM/ARMFastISel.cpp
+++ b/lib/Target/ARM/ARMFastISel.cpp
@@ -1151,6 +1151,12 @@ bool ARMFastISel::SelectBranch(const Instruction *I) {
       FuncInfo.MBB->addSuccessor(TBB);
       return true;
     }
+  } else if (const ConstantInt *CI =
+             dyn_cast<ConstantInt>(BI->getCondition())) {
+    uint64_t Imm = CI->getZExtValue();
+    MachineBasicBlock *Target = (Imm == 0) ? FBB : TBB;
+    FastEmitBranch(Target, DL);
+    return true;
   }
 
   unsigned CmpReg = getRegForValue(BI->getCondition());
diff --git a/test/CodeGen/ARM/fast-isel-br-const.ll b/test/CodeGen/ARM/fast-isel-br-const.ll
new file mode 100644
index 00000000000..b7acfaab22f
--- /dev/null
+++ b/test/CodeGen/ARM/fast-isel-br-const.ll
@@ -0,0 +1,47 @@
+; RUN: llc < %s -O0 -fast-isel-abort -relocation-model=dynamic-no-pic -mtriple=armv7-apple-darwin | FileCheck %s --check-prefix=ARM
+; RUN: llc < %s -O0 -fast-isel-abort -relocation-model=dynamic-no-pic -mtriple=thumbv7-apple-darwin | FileCheck %s --check-prefix=THUMB
+
+define i32 @t1(i32 %a, i32 %b) nounwind uwtable ssp {
+entry:
+; THUMB: t1:
+; ARM: t1:
+
+  br i1 1, label %if.then, label %if.else
+; THUMB-NOT: b LBB0_1
+; ARM-NOT:  b LBB0_1
+
+if.then:                                          ; preds = %entry
+  call void @foo1()
+  br label %if.end7
+
+if.else:                                          ; preds = %entry
+  br i1 0, label %if.then2, label %if.else3
+; THUMB: b LBB0_4
+; ARM:  b LBB0_4
+
+if.then2:                                         ; preds = %if.else
+  call void @foo2()
+  br label %if.end6
+
+if.else3:                                         ; preds = %if.else
+  br i1 1, label %if.then5, label %if.end
+; THUMB-NOT: b LBB0_5
+; ARM-NOT:  b LBB0_5
+
+if.then5:                                         ; preds = %if.else3
+  call void @foo1()
+  br label %if.end
+
+if.end:                                           ; preds = %if.then5, %if.else3
+  br label %if.end6
+
+if.end6:                                          ; preds = %if.end, %if.then2
+  br label %if.end7
+
+if.end7:                                          ; preds = %if.end6, %if.then
+  ret i32 0
+}
+
+declare void @foo1()
+
+declare void @foo2()
-- 
2.34.1