[llvm-commits] [llvm] r66865 - in /llvm/trunk: lib/Target/X86/X86ISelDAGToDAG.cpp test/CodeGen/X86/fold-add.ll

[Dan Gohman]

Author: djg
Date: Thu Mar 12 21:25:09 2009
New Revision: 66865

URL: http://llvm.org/viewvc/llvm-project?rev=66865&view=rev
Log:
Enhance address-mode folding of ISD::ADD to handle cases where the
operands can't both be fully folded at the same time. For example,
in the included testcase, a global variable is being added with
an add of two values. The global variable wants RIP-relative
addressing, so it can't share the address with another base
register, but it's still possible to fold the initial add.

Added:
    llvm/trunk/test/CodeGen/X86/fold-add.ll
Modified:
    llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp

Modified: llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp?rev=66865&r1=66864&r2=66865&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp Thu Mar 12 21:25:09 2009
@@ -907,6 +907,19 @@
         !MatchAddress(N.getNode()->getOperand(0), AM, false, Depth+1))
       return false;
     AM = Backup;
+
+    // If we couldn't fold both operands into the address at the same time,
+    // see if we can just put each operand into a register and fold at least
+    // the add.
+    if (AM.BaseType == X86ISelAddressMode::RegBase &&
+        !AM.Base.Reg.getNode() &&
+        !AM.IndexReg.getNode() &&
+        !AM.isRIPRel) {
+      AM.Base.Reg = N.getNode()->getOperand(0);
+      AM.IndexReg = N.getNode()->getOperand(1);
+      AM.Scale = 1;
+      return false;
+    }
     break;
   }
 

Added: llvm/trunk/test/CodeGen/X86/fold-add.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/fold-add.ll?rev=66865&view=auto

==============================================================================
--- llvm/trunk/test/CodeGen/X86/fold-add.ll (added)
+++ llvm/trunk/test/CodeGen/X86/fold-add.ll Thu Mar 12 21:25:09 2009
@@ -0,0 +1,25 @@
+; RUN: llvm-as < %s | llc -march=x86-64 | grep {cmpb	\$0, (%r.\*,%r.\*)}
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
+target triple = "x86_64-apple-darwin9.6"
+ at prev_length = internal global i32 0		; <i32*> [#uses=1]
+ at window = internal global [65536 x i8] zeroinitializer, align 32		; <[65536 x i8]*> [#uses=1]
+ at llvm.used = appending global [1 x i8*] [i8* bitcast (i32 (i32)* @longest_match to i8*)]		; <[1 x i8*]*> [#uses=0]
+
+define fastcc i32 @longest_match(i32 %cur_match) nounwind {
+entry:
+	%0 = load i32* @prev_length, align 4		; <i32> [#uses=3]
+	%1 = zext i32 %cur_match to i64		; <i64> [#uses=1]
+	%2 = sext i32 %0 to i64		; <i64> [#uses=1]
+	%.sum3 = add i64 %1, %2		; <i64> [#uses=1]
+	%3 = getelementptr [65536 x i8]* @window, i64 0, i64 %.sum3		; <i8*> [#uses=1]
+	%4 = load i8* %3, align 1		; <i8> [#uses=1]
+	%5 = icmp eq i8 %4, 0		; <i1> [#uses=1]
+	br i1 %5, label %bb5, label %bb23
+
+bb5:		; preds = %entry
+	ret i32 %0
+
+bb23:		; preds = %entry
+	ret i32 %0
+}