[ARMConstantIsland] Insert tbb/tbh optimization where previous jump table resided.

llvm-svn: 224165

2 files changed, 50 insertions, 1 deletions

diff --git a/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp b/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
index 29405eb65d5..634c04533a8 100644
--- a/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
+++ b/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -1952,7 +1952,9 @@ bool ARMConstantIslands::optimizeThumb2JumpTables() {
       DEBUG(dbgs() << "Shrink JT: " << *MI << "     addr: " << *AddrMI
                    << "      lea: " << *LeaMI);
       unsigned Opc = ByteOk ? ARM::t2TBB_JT : ARM::t2TBH_JT;
-      MachineInstr *NewJTMI = BuildMI(MBB, MI->getDebugLoc(), TII->get(Opc))
+      MachineBasicBlock::iterator MI_JT = MI;
+      MachineInstr *NewJTMI =
+        BuildMI(*MBB, MI_JT, MI->getDebugLoc(), TII->get(Opc))
         .addReg(IdxReg, getKillRegState(IdxRegKill))
         .addJumpTableIndex(JTI, JTOP.getTargetFlags())
         .addImm(MI->getOperand(JTOpIdx+1).getImm());
diff --git a/llvm/test/CodeGen/Thumb2/constant-islands-jump-table.ll b/llvm/test/CodeGen/Thumb2/constant-islands-jump-table.ll
new file mode 100644
index 00000000000..0dd7092291b
--- /dev/null
+++ b/llvm/test/CodeGen/Thumb2/constant-islands-jump-table.ll
@@ -0,0 +1,47 @@
+; RUN: llc < %s -mtriple=thumbv7-linux-gnueabihf -O1 %s -o - | FileCheck %s
+
+; CHECK-LABEL: test_jump_table:
+; CHECK: b .LBB
+; CHECK-NOT: tbh
+
+define i32 @test_jump_table(i32 %x, float %in) {
+
+h1:
+
+ %b0 = fadd float %in, 1234.5
+ %b1 = fptoui float %b0 to i32
+  
+  switch i32 %x, label %h2 [
+    i32 0, label %h3
+    i32 2, label %h4
+    i32 4, label %h5
+    i32 6, label %h6
+  ]
+
+h2:
+  %a0 = add i32 %x, 5
+  br label %h3
+
+h3:
+  %d2 = phi i32 [%b1, %h1], [%a0, %h2]
+  %d3 = add i32 %d2, 3
+  br label %h4
+
+h4:
+  %c2 = phi i32 [%b1, %h1], [%d3, %h3]
+  %c3 = add i32 %c2, 5
+  br label %h5
+
+h5:
+  %a2 = phi i32 [%b1, %h1], [%c3, %h4]
+  %a3 = add i32 %a2, 6
+  br label %h6
+
+h6:
+  %y = phi i32 [0, %h1], [%a3, %h5]
+  call i32 @llvm.arm.space(i32 2000, i32 undef)
+  ret i32 %y
+  
+}
+
+declare i32 @llvm.arm.space(i32, i32)