Teach branch folding pass about implicit_def instructions. Unfortunately we can't just eliminate them since register scavenger expects every register use to be defined. However, we can delete them when there are no intra-block uses. Carefully removing some implicit def's which enable more blocks to be optimized away.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49461 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 48 insertions, 0 deletions

diff --git a/test/CodeGen/X86/2008-04-09-BranchFolding.ll b/test/CodeGen/X86/2008-04-09-BranchFolding.ll
new file mode 100644
index 0000000..fea54c4
--- /dev/null
+++ b/test/CodeGen/X86/2008-04-09-BranchFolding.ll
@@ -0,0 +1,48 @@
+; RUN: llvm-as < %s | llc -march=x86 | not grep jmp
+
+	%struct..0anon = type { i32 }
+	%struct.binding_level = type { %struct.tree_node*, %struct.tree_node*, %struct.tree_node*, %struct.tree_node*, %struct.tree_node*, %struct.binding_level*, i8, i8, i8, i8, i8, i32, %struct.tree_node* }
+	%struct.lang_decl = type opaque
+	%struct.rtx_def = type { i16, i8, i8, [1 x %struct..0anon] }
+	%struct.tree_decl = type { [12 x i8], i8*, i32, %struct.tree_node*, i32, i8, i8, i8, i8, %struct.tree_node*, %struct.tree_node*, %struct.tree_node*, %struct.tree_node*, %struct.tree_node*, %struct.tree_node*, %struct.tree_node*, %struct.tree_node*, %struct.tree_node*, %struct.rtx_def*, %struct..0anon, { %struct.rtx_def* }, %struct.tree_node*, %struct.lang_decl* }
+	%struct.tree_node = type { %struct.tree_decl }
+
+define fastcc %struct.tree_node* @pushdecl(%struct.tree_node* %x) nounwind  {
+entry:
+	%tmp3.i40 = icmp eq %struct.binding_level* null, null		; <i1> [#uses=2]
+	br i1 false, label %bb143, label %bb140
+bb140:		; preds = %entry
+	br i1 %tmp3.i40, label %bb160, label %bb17.i
+bb17.i:		; preds = %bb140
+	ret %struct.tree_node* null
+bb143:		; preds = %entry
+	%tmp8.i43 = load %struct.tree_node** null, align 4		; <%struct.tree_node*> [#uses=1]
+	br i1 %tmp3.i40, label %bb160, label %bb9.i48
+bb9.i48:		; preds = %bb143
+	ret %struct.tree_node* null
+bb160:		; preds = %bb143, %bb140
+	%t.0.reg2mem.0 = phi %struct.tree_node* [ null, %bb140 ], [ %tmp8.i43, %bb143 ]		; <%struct.tree_node*> [#uses=1]
+	%tmp162 = icmp eq %struct.tree_node* %t.0.reg2mem.0, null		; <i1> [#uses=2]
+	br i1 %tmp162, label %bb174, label %bb165
+bb165:		; preds = %bb160
+	br label %bb174
+bb174:		; preds = %bb165, %bb160
+	%line.0 = phi i32 [ 0, %bb165 ], [ undef, %bb160 ]		; <i32> [#uses=1]
+	%file.0 = phi i8* [ null, %bb165 ], [ undef, %bb160 ]		; <i8*> [#uses=1]
+	br i1 %tmp162, label %bb344, label %bb73.i
+bb73.i:		; preds = %bb174
+	br i1 false, label %bb226.i, label %bb220.i
+bb220.i:		; preds = %bb73.i
+	ret %struct.tree_node* null
+bb226.i:		; preds = %bb73.i
+	br i1 false, label %bb260, label %bb273.i
+bb273.i:		; preds = %bb226.i
+	ret %struct.tree_node* null
+bb260:		; preds = %bb226.i
+	tail call void (i8*, i32, ...)* @pedwarn_with_file_and_line( i8* %file.0, i32 %line.0, i8* null ) nounwind 
+	ret %struct.tree_node* null
+bb344:		; preds = %bb174
+	ret %struct.tree_node* null
+}
+
+declare void @pedwarn_with_file_and_line(i8*, i32, ...) nounwind