From 5e8d9def77b4a68e6be32f21cda28d2a451267a9 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Sat, 20 Sep 2008 01:28:05 +0000
Subject: [PATCH] Fix PR2808. When regalloc runs out of register, it spill a
 physical register around the live interval being allocated. Do not continue
 to try to spill another register, just grab the physical register and move
 on.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56381 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/RegAllocLinearScan.cpp         |  5 ++++-
 test/CodeGen/X86/2008-09-19-RegAllocBug.ll | 22 ++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/X86/2008-09-19-RegAllocBug.ll

diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index 000dd41b97a..df9d393a8f4 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -855,9 +855,12 @@ void RALinScan::assignRegOrStackSlotAtInterval(LiveInterval* cur)
     // All registers must have inf weight. Just grab one!
     minReg = BestPhysReg ? BestPhysReg : *RC->allocation_order_begin(*mf_);
     if (cur->weight == HUGE_VALF ||
-        li_->getApproximateInstructionCount(*cur) == 0)
+        li_->getApproximateInstructionCount(*cur) == 0) {
       // Spill a physical register around defs and uses.
       li_->spillPhysRegAroundRegDefsUses(*cur, minReg, *vrm_);
+      assignRegOrStackSlotAtInterval(cur);
+      return;
+    }
   }
 
   // Find up to 3 registers to consider as spill candidates.
diff --git a/test/CodeGen/X86/2008-09-19-RegAllocBug.ll b/test/CodeGen/X86/2008-09-19-RegAllocBug.ll
new file mode 100644
index 00000000000..47feb83c927
--- /dev/null
+++ b/test/CodeGen/X86/2008-09-19-RegAllocBug.ll
@@ -0,0 +1,22 @@
+; RUN: llvm-as < %s | llc -mtriple=i386-apple-darwin
+; PR2808
+
+@g_3 = external global i32		; <i32*> [#uses=1]
+
+define i32 @func_4() nounwind {
+entry:
+	%0 = load i32* @g_3, align 4		; <i32> [#uses=2]
+	%1 = trunc i32 %0 to i8		; <i8> [#uses=1]
+	%2 = sub i8 1, %1		; <i8> [#uses=1]
+	%3 = sext i8 %2 to i32		; <i32> [#uses=1]
+	%.0 = ashr i32 %3, select (i1 icmp ne (i8 zext (i1 icmp ugt (i32 ptrtoint (i32 ()* @func_4 to i32), i32 3) to i8), i8 0), i32 0, i32 ptrtoint (i32 ()* @func_4 to i32))		; <i32> [#uses=1]
+	%4 = urem i32 %0, %.0		; <i32> [#uses=1]
+	%5 = icmp eq i32 %4, 0		; <i1> [#uses=1]
+	br i1 %5, label %return, label %bb4
+
+bb4:		; preds = %entry
+	ret i32 undef
+
+return:		; preds = %entry
+	ret i32 undef
+}