switch TargetLowering::getConstraintType to take the entire constraint,

[oota-llvm.git] / lib / Target / README.txt

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index 437e93c18c7089e7145cefe1a6154ff250e82d2d..8297bc3a8c8f781f43ea5a6542f73e3494a0c785 100644 (file)
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -20,12 +20,14 @@ This has a number of uses:
 
 FreeBench/mason contains code like this:
 
-static p_type m0u(p_type p) {
+typedef struct { int a; int b; int c; } p_type;
+extern int m[];
+p_type m0u(p_type *p) {
   int m[]={0, 8, 1, 2, 16, 5, 13, 7, 14, 9, 3, 4, 11, 12, 15, 10, 17, 6};
   p_type pu;
-  pu.a = m[p.a];
-  pu.b = m[p.b];
-  pu.c = m[p.c];
+  pu.a = m[p->a];
+  pu.b = m[p->b];
+  pu.c = m[p->c];
   return pu;
 }
 
@@ -122,10 +124,6 @@ for 1,2,4,8 bytes.
 
 //===---------------------------------------------------------------------===//
 
-Add LSR exit value substitution. It'll probably be a win for Ackermann, etc.
-
-//===---------------------------------------------------------------------===//
-
 It would be nice to revert this patch:
 http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20060213/031986.html
 
@@ -348,46 +346,6 @@ pass.
 
 //===---------------------------------------------------------------------===//
 
--predsimplify should transform this:
-
-void bad(unsigned x)
-{
-  if (x > 4)
-    bar(12);
-  else if (x > 3)
-    bar(523);
-  else if (x > 2)
-    bar(36);
-  else if (x > 1)
-    bar(65);
-  else if (x > 0)
-    bar(45);
-  else
-    bar(367);
-}
-
-into:
-
-void good(unsigned x)
-{
-  if (x == 4)
-    bar(523);
-  else if (x == 3)
-    bar(36);
-  else if (x == 2)
-    bar(65);
-  else if (x == 1)
-    bar(45);
-  else if (x == 0)
-    bar(367);
-  else
-    bar(12);
-}
-
-to enable further optimizations.
-
-//===---------------------------------------------------------------------===//
-
 Consider:
 
 typedef unsigned U32;
@@ -419,3 +377,35 @@ Promote for i32 bswap can use i64 bswap + shr.  Useful on targets with 64-bit
 regs and bswap, like itanium.
 
 //===---------------------------------------------------------------------===//
+
+LSR should know what GPR types a target has.  This code:
+
+volatile short X, Y; // globals
+
+void foo(int N) {
+  int i;
+  for (i = 0; i < N; i++) { X = i; Y = i*4; }
+}
+
+produces two identical IV's (after promotion) on PPC/ARM:
+
+LBB1_1: @bb.preheader
+        mov r3, #0
+        mov r2, r3
+        mov r1, r3
+LBB1_2: @bb
+        ldr r12, LCPI1_0
+        ldr r12, [r12]
+        strh r2, [r12]
+        ldr r12, LCPI1_1
+        ldr r12, [r12]
+        strh r3, [r12]
+        add r1, r1, #1    <- [0,+,1]
+        add r3, r3, #4
+        add r2, r2, #1    <- [0,+,1]
+        cmp r1, r0
+        bne LBB1_2      @bb
+
+
+//===---------------------------------------------------------------------===//
+