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8361836: RISC-V: Relax min vector length to 32-bit for short vectors #26239

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8361836: RISC-V: Relax min vector length to 32-bit for short vectors #26239

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8361836: RISC-V: Relax min vector length to 32-bit for short vectors
DingliZhang Jul 10, 2025
0773a36
Adjust the position of comment
DingliZhang Jul 10, 2025
84d6b25
Use switch-case in min_vector_size
DingliZhang Jul 15, 2025
7120525
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DingliZhang Jul 15, 2025
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34 changes: 24 additions & 10 deletions src/hotspot/cpu/riscv/riscv.ad
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Original file line number Diff line number Diff line change
Expand Up @@ -1985,17 +1985,31 @@ int Matcher::max_vector_size(const BasicType bt) {
}

int Matcher::min_vector_size(const BasicType bt) {
int max_size = max_vector_size(bt);
// Limit the min vector size to 8 bytes.
int size = 8 / type2aelembytes(bt);
if (bt == T_BYTE) {
// To support vector api shuffle/rearrange.
size = 4;
} else if (bt == T_BOOLEAN) {
// To support vector api load/store mask.
size = 2;
int size;
switch(bt) {
case T_BOOLEAN:
// Load/store a vector mask with only 2 elements for vector types
// such as "2I/2F/2L/2D".
size = 2;
break;
case T_BYTE:
// Generate a "4B" vector, to support vector cast between "8B/16B"
// and "4S/4I/4L/4F/4D".
size = 4;
break;
case T_SHORT:
// Generate a "2S" vector, to support vector cast between "4S/8S"
// and "2I/2L/2F/2D".
size = 2;
break;
default:
// Limit the min vector length to 64-bit.
size = 8 / type2aelembytes(bt);
// The number of elements in a vector should be at least 2.
size = MAX2(size, 2);
}
if (size < 2) size = 2;

int max_size = max_vector_size(bt);
return MIN2(size, max_size);
}

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15 changes: 15 additions & 0 deletions test/hotspot/jtreg/compiler/vectorapi/reshape/utils/TestCastMethods.java
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Original file line number Diff line number Diff line change
Expand Up @@ -127,11 +127,17 @@ public class TestCastMethods {
// from S 64
// to X 64
makePair(SSPEC64, BSPEC64),
makePair(SSPEC64, ISPEC64),
makePair(SSPEC64, ISPEC64, true),
makePair(SSPEC64, FSPEC64),
// to X 128
makePair(SSPEC64, BSPEC128),
makePair(SSPEC64, ISPEC128),
makePair(SSPEC64, ISPEC128, true),
makePair(SSPEC64, LSPEC128),
makePair(SSPEC64, LSPEC128, true),
makePair(SSPEC64, FSPEC128),
makePair(SSPEC64, DSPEC128),
// to X 256
makePair(SSPEC64, BSPEC256),
makePair(SSPEC64, ISPEC256),
Expand All @@ -156,7 +162,10 @@ public class TestCastMethods {
makePair(SSPEC128, BSPEC128),
makePair(SSPEC128, ISPEC128),
makePair(SSPEC128, ISPEC128, true),
makePair(SSPEC128, LSPEC128),
makePair(SSPEC128, LSPEC128, true),
makePair(SSPEC128, FSPEC128),
makePair(SSPEC128, DSPEC128),
// to X 256
makePair(SSPEC128, BSPEC256),
makePair(SSPEC128, ISPEC256),
Expand Down Expand Up @@ -228,6 +237,7 @@ public class TestCastMethods {
// ====== from I ======
// from I 64
// to X 64
makePair(ISPEC64, SSPEC64),
makePair(ISPEC64, FSPEC64),
// to X 128
makePair(ISPEC64, LSPEC128),
Expand Down Expand Up @@ -299,10 +309,12 @@ public class TestCastMethods {
// ====== from L ======
// from L 128
// to X 64
makePair(LSPEC128, SSPEC64),
makePair(LSPEC128, ISPEC64),
makePair(LSPEC128, FSPEC64),
makePair(LSPEC128, DSPEC64),
// to X 128
makePair(LSPEC128, SSPEC128),
makePair(LSPEC128, ISPEC128),
makePair(LSPEC128, FSPEC128),
makePair(LSPEC128, DSPEC128),
Expand Down Expand Up @@ -369,6 +381,7 @@ public class TestCastMethods {
// ====== from F ======
// from F 64
// to X 64
makePair(FSPEC64, SSPEC64),
makePair(FSPEC64, ISPEC64),
// to X 128
makePair(FSPEC64, ISPEC128),
Expand Down Expand Up @@ -433,10 +446,12 @@ public class TestCastMethods {
// ====== from D ======
// from D 128
// to X 64
makePair(DSPEC128, SSPEC64),
makePair(DSPEC128, ISPEC64),
makePair(DSPEC128, LSPEC64),
makePair(DSPEC128, FSPEC64),
// to X 128
makePair(DSPEC128, SSPEC128),
makePair(DSPEC128, ISPEC128),
makePair(DSPEC128, LSPEC128),
makePair(DSPEC128, FSPEC128),
Expand Down