From 456861c11559bd2cc2a1cffdb0037c1a6f97e289 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Fri, 22 Dec 2006 23:14:42 +0000
Subject: [PATCH] add a simple fast-path for dead allocas

llvm-svn: 32750
---
 lib/Transforms/Scalar/ScalarReplAggregates.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
index 160128eba1d..a92592b8166 100644
--- a/lib/Transforms/Scalar/ScalarReplAggregates.cpp
+++ b/lib/Transforms/Scalar/ScalarReplAggregates.cpp
@@ -139,6 +139,13 @@ bool SROA::performScalarRepl(Function &F) {
     AllocationInst *AI = WorkList.back();
     WorkList.pop_back();
     
+    // Handle dead allocas trivially.  These can be formed by SROA'ing arrays
+    // with unused elements.
+    if (AI->use_empty()) {
+      AI->eraseFromParent();
+      continue;
+    }
+    
     // If we can turn this aggregate value (potentially with casts) into a
     // simple scalar value that can be mem2reg'd into a register value.
     bool IsNotTrivial = false;
@@ -232,7 +239,7 @@ bool SROA::performScalarRepl(Function &F) {
     }
 
     // Finally, delete the Alloca instruction
-    AI->getParent()->getInstList().erase(AI);
+    AI->eraseFromParent();
     NumReplaced++;
   }