R600: Fix a crash in the AMDILCFGStructurizer

We were calling llvm_unreachable() when failing to optimize the
branch into if case.  However, it is still possible for us
to structurize the CFG by duplicating blocks even if this optimization
fails.

Reviewed-by: Vincent Lejeune<vljn at ovi.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192813 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 83 insertions, 0 deletions

diff --git a/test/CodeGen/R600/structurize.ll b/test/CodeGen/R600/structurize.ll
new file mode 100644
index 0000000..b955619
--- /dev/null
+++ b/test/CodeGen/R600/structurize.ll
@@ -0,0 +1,83 @@
+; RUN: llc < %s -march=r600 -mcpu=redwood | FileCheck %s
+; Test case for a crash in the AMDILCFGStructurizer from a CFG like this:
+;
+;                            entry
+;                           /     \
+;               diamond_head       branch_from
+;                 /      \           |
+;    diamond_false        diamond_true
+;                 \      /
+;                   done
+;
+; When the diamond_true branch had more than 100 instructions.
+;
+;
+
+; CHECK-LABEL: @branch_into_diamond
+; === entry block:
+; CHECK: ALU_PUSH_BEFORE
+; === Branch instruction (IF):
+; CHECK: JUMP
+  ; === branch_from block
+  ; CHECK: ALU
+  ; === Duplicated diamond_true block (There can be more than one ALU clause):
+  ; === XXX: We should be able to optimize this so the basic block is not
+  ; === duplicated.  See comments in
+  ; === AMDGPUCFGStructurizer::improveSimpleJumpintoIf()
+  ; CHECK: ALU
+; === Branch instruction (ELSE):
+; CHECK: ELSE
+  ; === diamond_head block:
+  ; CHECK: ALU_PUSH_BEFORE
+  ; === Branch instruction (IF):
+  ; CHECK: JUMP
+    ; === diamond_true block (There can be more than one ALU clause):
+    ; ALU
+  ; === Branch instruction (ELSE):
+  ; CHECK: ELSE
+    ; === diamond_false block plus implicit ENDIF
+    ; CHECK: ALU_POP_AFTER
+; === Branch instruction (ENDIF):
+; CHECK: POP
+; === done block:
+; CHECK: ALU
+; CHECK: MEM_RAT_CACHELESS
+; CHECK: CF_END
+
+
+define void @branch_into_diamond(i32 addrspace(1)* %out, i32 %a, i32 %b, i32 %c) {
+entry:
+%0 = icmp ne i32 %a, 0
+  br i1 %0, label %diamond_head, label %branch_from
+
+diamond_head:
+  %1 = icmp ne i32 %a, 1
+  br i1 %1, label %diamond_true, label %diamond_false
+
+branch_from:
+  %2 = add i32 %a, 1
+  br label %diamond_true
+
+diamond_false:
+  %3 = add i32 %a, 2
+  br label %done
+
+diamond_true:
+  %4 = phi i32 [%2, %branch_from], [%a, %diamond_head]
+  ; This block needs to be > 100 ISA instructions to hit the bug,
+  ; so we'll use udiv instructions.
+  %div0 = udiv i32 %a, %b
+  %div1 = udiv i32 %div0, %4
+  %div2 = udiv i32 %div1, 11
+  %div3 = udiv i32 %div2, %a
+  %div4 = udiv i32 %div3, %b
+  %div5 = udiv i32 %div4, %c
+  %div6 = udiv i32 %div5, %div0
+  %div7 = udiv i32 %div6, %div1
+  br label %done
+
+done:
+  %5 = phi i32 [%3, %diamond_false], [%div7, %diamond_true]
+  store i32 %5, i32 addrspace(1)* %out
+  ret void
+}